The Collaborative International Dictionary of English v.0.48:

Flagellate \Flag"el*late\, v. t. [imp. & p. p. Flagellated; p.
   pr. & vb. n. Flagellating.] [L. flagellatus, p. p. of
   flagellare to scoure, fr. flagellum whip, dim. of flagrum
   whip, scoure; cf. fligere to strike. Cf. Flall.]
   To whip; to scourge; to flog.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Flagellate \Fla*gel"late\, a.
   1. Flagelliform.
      [1913 Webster]

   2. (Zool.) Of or pertaining to the Flagellata.
      [1913 Webster]

   3. Having a flagellum or flagella.
      [PJC]

WordNet (r) 3.0 (2006):

flagellate
    adj 1: having or resembling a lash or whip (as does a flagellum)
           [syn: flagellate, flagellated, whiplike, lash-
           like]
    n 1: a usually nonphotosynthetic free-living protozoan with
         whiplike appendages; some are pathogens of humans and other
         animals [syn: flagellate, flagellate protozoan,
         flagellated protozoan, mastigophoran, mastigophore]
    v 1: whip; "The religious fanatics flagellated themselves" [syn:
         flagellate, scourge]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "flagellate":
   baste, bastinado, beat, belabor, belt, birch, buffet, cane, club,
   cowhide, cudgel, cut, drub, flail, flog, fustigate,
   give a whipping, give the stick, hide, horsewhip, knout, lace,
   larrup, lash, lay on, pistol-whip, pommel, pummel, rawhide,
   scourge, smite, spank, strap, stripe, swinge, switch, thrash,
   thump, trounce, truncheon, wallop, whale, whip, whop