flagellum

A whiplike locomotory organelle of constant structural arrangement consisting of nine double peripheral microtubules and two single central microtubules; it arises from a deeply staining basal granule, often connected to the nucleus by a fiber, the rhizoplast. Though characteristic of the protozoan class Mastigophora, comparable structures are commonly found in many other groups, e.g., in spermatozoa. [L. dim. of flagrum, a whip]

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fla·gel·lum flə-'jel-əm n, pl -la -ə also -lums a long tapering process that projects singly or in groups from a cell and is the primary organ of motion of many microorganisms

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n. (pl. flagella)

a fine long whiplike thread attached to certain types of cell (e.g. spermatozoa and some unicellular organisms). Flagella are responsible for the movement of the organisms to which they are attached.

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fla·gel·lum (flə-jelґəm) pl. flagelґla [L. “whip”] a long, mobile, whiplike projection from the free surface of a cell, serving as a locomotor organelle. In eukaryotes, it is composed of nine pairs of microtubules arrayed around a central pair. Arising from basal bodies, flagella are common to all mastigophoran protozoa and occur in such specialized cells as spermatozoa. Bacterial flagella are thinner and simpler, being composed of strands of flagellin tightly woven in a helical filament, attached to a basal body in the cell wall. Based on the configuration of their flagella, bacteria are characterized as either monotrichous, lophotrichous, amphitrichous, or peritrichous. See also cilia (def. 3). flagellar adj