The Collaborative International Dictionary of English v.0.48:

Crater \Cra"ter\ (kr[=a]"t[~e]r), n. [L. crater, cratera, a
   mixing vessel, the mouth of a volcano, Gr. krath`r, fr.
   keranny`nai to mix; cf. Skr. [,c]r[imac] to mix, [,c]ir to
   cook, [,c]r[=a] to cook. Cf. Grail, in Holy Grail.]
   1. The basinlike opening or mouth of a volcano, through which
      the chief eruption comes; similarly, the mouth of a
      geyser, about which a cone of silica is often built up.
      [1913 Webster]

   2. (Mil.) The pit left by the explosion of a bomb, shell, or
      mine.
      [1913 Webster]

   3. (Astron.) A constellation of the southen hemisphere; --
      called also the Cup.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "crater":
   abysm, abyss, alveolation, alveolus, antrum, armpit, basin,
   birthmark, blackhead, bleb, blemish, blister, bowl, bulla, cavity,
   chasm, check, cicatrix, comedo, concave, concavity, crack, craze,
   crevasse, crypt, cup, deep, defacement, defect, deformation,
   deformity, depression, depth, dip, disfiguration, disfigurement,
   distortion, fault, flaw, fold, follicle, freckle, funnel chest,
   gulf, hemangioma, hickey, hole, hollow, hollow shell, keloid, kink,
   lacuna, lentigo, milium, mole, needle scar, nevus, pimple, pit,
   pock, pocket, pockmark, port-wine mark, port-wine stain,
   punch bowl, pustule, rift, scab, scar, scoop, scratch,
   sebaceous cyst, shaft, shell, sink, sinus, socket, split,
   strawberry mark, sty, track, trough, twist, verruca, vesicle, vug,
   wale, warp, wart, weal, well, welt, wen, whitehead,
   yawning abyss