The Collaborative International Dictionary of English v.0.48:

Bufferin \Bufferin\ n. [trademark.]
   a brand of aspirin tablets coated with a substance capable
   of neutralizing acid (a "buffer"); -- sometimes applied
   generically to any buffered aspirin preparation.

   Syn: buffered aspirin.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Bufferin
    n 1: aspirin coated with a substance capable of neutralizing
         acid (trade name Bufferin) [syn: buffered aspirin,
         Bufferin]