The Collaborative International Dictionary of English v.0.48:

Pimple \Pim"ple\, n. [AS. p[imac]pelian to blister; cf. L.
   papula pimple.]
   1. (Med.) Any small acuminated elevation of the cuticle,
      whether going on to suppuration or not. "All eyes can see
      a pimple on her nose." --Pope.
      [1913 Webster]

   2. Fig.: A swelling or protuberance like a pimple. "A pimple
      that portends a future sprout." --Cowper.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pimple
    n 1: a small inflamed elevation of the skin; a pustule or
         papule; common symptom in acne [syn: pimple, hickey,
         zit]

Moby Thesaurus II by Grady Ward, 1.0:

172 Moby Thesaurus words for "pimple":
   abscess, aposteme, bed sore, birthmark, blackhead, blain, bleb,
   blemish, blister, boil, boss, bubo, bulla, bump, bunion, canker,
   canker sore, carbuncle, chancre, chancroid, check, chilblain,
   cicatrix, coarsen, cold sore, colophon, comedo, concavity,
   convexity, corn, crack, crater, craze, cyst, dactylogram,
   dactylograph, defacement, defect, deformation, deformity, dent,
   dilatation, dilation, dint, disfiguration, disfigurement,
   distension, distortion, dot, edema, embossment, eruption, eschar,
   excrescence, fault, felon, fester, festering, fever blister,
   fingerprint, fistula, flaw, footmark, footprint, footstep,
   fossil footprint, freckle, furuncle, furunculus, gathering, gnarl,
   granulate, gumboil, hemangioma, hemorrhoids, hickey, horripilate,
   ichnite, ichnolite, impress, impression, imprint, indent,
   indentation, indention, intumescence, keloid, kibe, kink, knob,
   lentigo, lesion, lump, milium, mole, needle scar, nevus, pad,
   papula, papule, paronychia, parulis, paw print, pawmark, petechia,
   piles, pit, pock, pockmark, polyp, port-wine mark, port-wine stain,
   print, pug, pugmark, pustule, rift, rising, rough, rough up,
   roughen, scab, scar, scratch, seal, sebaceous cyst, sigil, signet,
   soft chancre, sore, speckle, split, spot, sprinkle, stamp, step,
   stigma, strawberry mark, stud, sty, suppuration, swell, swelling,
   swollenness, thumbmark, thumbprint, track, tubercle, tumefaction,
   tumescence, tumidity, tumor, turgescence, turgescency, turgidity,
   twist, ulcer, ulceration, verruca, vesicle, vestige, wale, warp,
   wart, weal, welt, wen, wheal, whelk, whitehead, whitlow, wound