flagellum

noun

(L. flagellum: whip) (pl. flagella) Any of various elongated filiform appendages of plants or animals: as the slender distal part of an antenna or a long tapering process that projects singly or in groups from a cell and is the primary organ of motion of many microorganisms. A tiny whiplike appendage, capable of movement. In prokaryotes: a long slender threadlike structure that protrudes from the cell surface of a bacterium. It rotates from its base and propels the bacterium along; up to several micrometres in length, a flagellum is constructed of numerous subunits of the protein flagellin flange, See also: undulipodium.