The Collaborative International Dictionary of English v.0.48:

Kneel \Kneel\ (n[=e]l), v. i. [imp. & p. p. Knelt (n[e^]lt) or
   Kneeled (n[=e]ld); p. pr. & vb. n. Kneeling.] [OE.
   knelen, cneolien; akin to D. knielen, Dan. kn[ae]le. See
   Knee.]
   To bend the knee; to fall or rest on the knees; -- sometimes
   with down.
   [1913 Webster]

   Note: The act of kneeling, when performed in front of a
         person, is often done as a sign of respect, humility,
         or supplication. It has a similar significance when
         performed in front of religious objects, such as an
         altar or shrine.
         [PJC]

               And he kneeled down, and cried with a loud voice,
               Lord, lay not this sin to their charge. --Acts
                                                  vii. 60.
         [1913 Webster]

               As soon as you are dressed, kneel and say the
               Lord's Prayer.                     --Jer. Taylor.
         [1913 Webster]

WordNet (r) 3.0 (2006):

kneel
    n 1: supporting yourself on your knees [syn: kneel,
         kneeling]
    v 1: rest one's weight on one's knees; "In church you have to
         kneel during parts of the service"

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "kneel":
   bend, bend the knee, bend the neck, bob, bob a curtsy, bob down,
   bootlick, bow, bow and scrape, bow down, bow the head, cower,
   crawl, creep, cringe, crouch, curtsy, duck, fall down before, fawn,
   flatter, genuflect, grovel, kowtow, lick the dust, lickspittle,
   make a leg, make a reverence, make obeisance, nod, salaam, scrape,
   stoop, toadeat, toady, truckle