The Collaborative International Dictionary of English v.0.48:

Cleave \Cleave\ (kl[=e]v), v. t. [imp. Cleft (kl[e^]ft),
   Clave (kl[=a]v, Obs.), Clove (kl[=o]v, Obsolescent); p.
   p. Cleft, Cleaved (kl[=e]vd) or Cloven (kl[=o]"v'n); p.
   pr. & vb. n. Cleaving.] [OE. cleoven, cleven, AS.
   cle['o]fan; akin to OS. klioban, D. klooven, G. klieben,
   Icel. klj[=u]fa, Sw. klyfva, Dan. kl["o]ve and prob. to Gr.
   gly`fein to carve, L. glubere to peel. Cf. Cleft.]
   1. To part or divide by force; to split or rive; to cut.
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            O Hamlet, thou hast cleft my heart in twain. --Shak.
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   2. To part or open naturally; to divide.
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            Every beast that parteth the hoof, and cleaveth the
            cleft into two claws.                 --Deut. xiv.
                                                  6.
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The Collaborative International Dictionary of English v.0.48:

Cleft \Cleft\ (kl[e^]ft),
   imp. & p. p. from Cleave.
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The Collaborative International Dictionary of English v.0.48:

Cleft \Cleft\, a.
   1. Divided; split; partly divided or split.
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   2. (Bot.) Incised nearly to the midrib; as, a cleft leaf.
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The Collaborative International Dictionary of English v.0.48:

Cleft \Cleft\, n. [OE. clift; cf. Sw. klyft cave, den, Icel.
   kluft cleft, Dan. kl["o]ft, G. kluft. See Cleave to split
   and cf. 2d Clift, 1st Clough.]
   1. A space or opening made by splitting; a crack; a crevice;
      as, the cleft of a rock. --Is. ii. 21.
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   2. A piece made by splitting; as, a cleft of wood.
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   3. (Far.) A disease in horses; a crack on the band of the
      pastern.
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   Branchial clefts. See under Branchial.

   Syn: Crack; crevice; fissure; chink; cranny.
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WordNet (r) 3.0 (2006):

cleft
    adj 1: having one or more incisions reaching nearly to the
           midrib [syn: cleft, dissected]
    n 1: a split or indentation in something (as the palate or chin)
    2: a long narrow opening [syn: crack, cleft, crevice,
       fissure, scissure]

Moby Thesaurus II by Grady Ward, 1.0:

171 Moby Thesaurus words for "cleft":
   abysm, abyss, alienation, aperture, arroyo, bifurcated, bisected,
   blaze, box canyon, branched, branching, breach,
   breach of friendship, break, breakage, broaching, burst, canyon,
   cavity, chap, chasm, check, chimney, chink, chinky, chip, clearing,
   cleavage, cleuch, clough, clove, cloven, col, coulee, couloir,
   crack, cracked, cranny, crena, crevasse, crevice, cut, cwm, defile,
   dehiscent, dell, depression, dichotomous, dike, dimidiate,
   disaffection, disclosure, disfavor, disruption, disunion, disunity,
   ditch, divergence, divided, dividedness, division, donga, draw,
   estrangement, excavation, falling-out, fault, fenestra, fissure,
   fissured, fissury, fistula, flaw, flume, fontanel, foramen, forked,
   forking, fracture, furrow, gap, gape, gaping, gappy, gash, gat,
   gorge, groove, gulch, gulf, gully, hack, halved, hiatus, hole,
   hollow, in pieces, in shreds, incision, indentation, inlet,
   interval, jag, jog, joggle, joint, kerf, kloof, lacerate,
   lacerated, lacuna, laying open, leak, mangled, moat, mutilated,
   nick, nock, notch, nullah, open rupture, opening, opening up,
   orifice, outlet, pass, passage, passageway, pore, quartered,
   ragged, ramified, ravine, recall of ambassadors, rent, rift, rime,
   rimose, rimulose, rip, riven, rupture, scale, schism, scissure,
   score, scotch, seam, separation, severed, shredded, slash, slice,
   slit, slot, space, splinter, splintered, split, stoma, tattered,
   tear, throwing open, torn, trench, uncorking, unstopping, valley,
   void, wadi, yawn