flagellum
fla.gel.lum \fl*-'jel-*m\ \-*\ n or fla.gel.la also flagellums [NL, fr. L, whip, shoot of a plant] pl : any of various elongated filiform appendages : as : the slender distal part of an antenna : a long tapering process that projects singly or in groups from a cell a nd is the primary organ of motion of many microorganisms : a long slender shoot