The Collaborative International Dictionary of English v.0.48:

Bleb \Bleb\, n. [Prov. E. bleb, bleib, blob, bubble, blister.
   This word belongs to the root of blub, blubber, blabber, and
   perh. blow to puff.]
   A large vesicle or bulla, usually containing a serous fluid;
   a blister; a bubble, as in water, glass, etc.
   [1913 Webster]

         Arsenic abounds with air blebs.          --Kirwan.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bleb
    n 1: (pathology) an elevation of the skin filled with serous
         fluid [syn: blister, bulla, bleb]

Moby Thesaurus II by Grady Ward, 1.0:

159 Moby Thesaurus words for "bleb":
   abscess, air bubble, aposteme, balloon, bed sore, bilge, birthmark,
   blackhead, bladder, blain, blemish, blister, blob, blood blister,
   boil, boss, bow, bubble, bubo, bulb, bulge, bulla, bump, bunch,
   bunion, burl, button, cahot, canker, canker sore, carbuncle,
   chancre, chancroid, check, chilblain, chine, cicatrix, clump,
   cold sore, comedo, condyle, convex, crack, crater, craze,
   defacement, defect, deformation, deformity, disfiguration,
   disfigurement, distortion, dowel, ear, eschar, fault, felon,
   fester, festering, fever blister, fistula, flange, flap, flaw,
   freckle, furuncle, furunculus, gall, gathering, globule, gnarl,
   gumboil, handle, hemangioma, hemorrhoids, hickey, hill, hump,
   hunch, jog, joggle, keloid, kibe, kink, knob, knot, knur, knurl,
   lentigo, lesion, lip, loop, lump, milium, mole, mountain,
   needle scar, nevus, nub, nubbin, nubble, papilloma, papula, papule,
   paronychia, parulis, peg, petechia, piles, pimple, pit, pock,
   pockmark, polyp, port-wine mark, port-wine stain, pustule, rib,
   ridge, rift, ring, rising, scab, scar, scratch, sebaceous cyst,
   shoulder, soap bubble, soft chancre, sore, spine, split, stigma,
   strawberry mark, stud, sty, style, suppuration, swelling, tab,
   track, tubercle, tubercule, twist, ulcer, ulceration, verruca,
   vesicle, wale, warp, wart, weal, welt, wen, wheal, whelk,
   whitehead, whitlow, wound