Glossary · Nouns · M
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TermTypeDefinitionClassificationsUpdated
Merinonounwhite sheep originating in Spain and producing a heavy fleece of exceptional qualityverified
Merino SheepnounMWEwhite sheep originating in Spain and producing a heavy fleece of exceptional qualityverified
Meristemnounundifferentiated tissue from which new cells are formed, as at the tip of a stem or rootverified
Merit PaynounMWEextra pay awarded to an employee on the basis of merit, especially to school teachersverified
Merit SystemnounMWEthe system of employing and promoting civil servants on the basis of abilityverified
Meritocracynounthe belief that rulers should be chosen for their superior abilities and not because of their wealth or birthverified
Merozoitenouna cell that arises from the asexual division of a parent sporozoan during its life cycleverified
Merry BellsnounMWEany of various plants of the genus Uvularia having yellowish drooping bell-shaped flowersverified
Merry-Go-Roundnouna never-ending cycle of activities and events (especially when they seem to have little purpose)verified
Mescalnouna colorless Mexican liquor distilled from fermented juices of certain desert plants of the genus Agavaceae (especially the century plant)verified
Mescal BeannounMWEshrub or small tree having pinnate leaves poisonous to livestock and dense racemes of intensely fragrant blue flowers and red beansverified
Mesenteric ArterynounMWEone of two branches of the aorta that pass between the two layers of the mesentery to the intestinesverified
Mesenteric VeinnounMWEa tributary of the portal vein passing from the intestine between the two layers of mesenteryverified
Mesenterynouna double layer of peritoneum that attaches to the back wall of the abdominal cavity and supports the small intestinesverified
Mesh TopologynounMWEthe topology of a network whose components are all connected directly to every other componentverified
Mesne LordnounMWEa feudal lord who was lord to his own tenants on land held from a superior lordverified
Mesoblastnounthe middle germ layer that develops into muscle and bone and cartilage and blood and connective tissueverified
Mesodermnounthe middle germ layer that develops into muscle and bone and cartilage and blood and connective tissueverified
Mesquitnounany of several small spiny trees or shrubs of the genus Prosopis having small flowers in axillary cylindrical spikes followed by large pods rich in sugarverified
Mesquitenounany of several small spiny trees or shrubs of the genus Prosopis having small flowers in axillary cylindrical spikes followed by large pods rich in sugarverified
Message authentication codenounMWEA cryptographic checksum on data that uses a symmetric key to detect both accidental and intentional modifications of the data. MACs provide authenticity and integrity protection, but not non-repudiation protection.Control
message contentnounMWEThe substantive payload of a communications unit — the data body conveying the actual information being sent — as opposed to routing and control metadata carried in headers. In information-flow enforcement contexts (NIST SP 800-53 AC-4, SP 800-171 control 03.01.03, CMMC AC.L2-3.1.3), it serves as the basis for deep inspection by boundary protection devices — gateways, firewalls, guards — that must look beyond header attributes (source/destination, port, protocol) to examine what a message actually says or contains, using techniques such as keyword searches or document-characteristic analysis, in order to make allow/deny decisions. Its defining role in security and compliance is thus to mark the boundary between shallow, metadata-based packet filtering and content-aware, payload-level filtering for information flow control, data loss prevention, and cross-domain security enforcement.Data
Message digestnounMWEA digital signature that uniquely identifies data and has the property that changing a single bit in the data will cause a completely different message digest to be generated.Data
Message digest algorithmnounMWEMessage digest algorithms are SHA1, MD2, MD4 and MD5. These algorithms are one-way functions unlike private and public key encryption algorithms. Scope Note: All digest algorithms take a message of arbitrary length and produce a 128-bit message digest.Capability
Message ExternalsnounMWEInformation outside of the message text, such as the header, trailer, etc.Data
Message IndicatornounMWESequence of bits transmitted over a communications system for synchronizing cryptographic equipment.DataRegulatedCUI
message-filtering capabilitynounMWEA control mechanism implemented in boundary protection devices — such as firewalls, guards, or cross-domain solutions — that inspects the *payload content* of communications (e.g., keyword matching, structural analysis, or document characteristics) to decide whether to allow, block, or transform an information flow, as distinguished from shallower approaches that act only on envelope or header metadata. In NIST's information-flow-enforcement framework, it sits alongside packet-filtering as one of the two primary enforcement modes, where packet-filtering acts on header information while message-filtering acts on message content; together they implement the policy that "regulates where information can travel within a system and between systems." Practical uses include blocking export-controlled information from leaving in the clear, restricting data transfers between organizations based on data structures and content, and enforcing boundary rules between security or privacy domains. The trustworthiness of the hardware, firmware, and software components performing that filtering is itself a security concern, and the control family extends to advanced cross-domain filtering techniquesControlRegulatedCUI
Messmatenoun(nautical) an associate with whom you share meals in the same mess (as on a ship)verified
Messuagenoun(law) a dwelling house and its adjacent buildings and the adjacent land used by the householdverified
Mestizanouna woman of mixed racial ancestry (especially mixed European and Native American ancestry)verified
Mestizonouna person of mixed racial ancestry (especially mixed European and Native American ancestry)verified
Mestranolnouna synthetic form of estrogen used in combination with a progestin in oral contraceptivesverified
Metabolic AcidosisnounMWEacidosis and bicarbonate concentration in the body fluids resulting either from the accumulation of acids or the abnormal loss of bases from the body (as in diarrhea or renal disease)verified
Metabolic AlkalosisnounMWEalkalosis resulting from hydrogen-ion loss or excessive intake of alkaline substancesverified
Metabolic ProcessnounMWEthe organic processes (in a cell or organism) that are necessary for lifeverified
Metabolismnounthe marked and rapid transformation of a larva into an adult that occurs in some animalsverified
Metabolitenounany substance involved in metabolism (either as a product of metabolism or as necessary for metabolism)verified