The Collaborative International Dictionary of English v.0.48:

Squash \Squash\, v. t. [imp. & p. p. Squashed (skw[o^]sht); p.
   pr. & vb. n. Squashing.] [OE. squachen, OF. escachier,
   esquachier, to squash, to crush, F. ['e]cacher, perhaps from
   (assumed) LL. excoacticare, fr. L. ex + coactare to
   constrain, from cogere, coactum, to compel. Cf. Cogent,
   Squat, v. i.]
   To beat or press into pulp or a flat mass; to crush.
   [1913 Webster]

WordNet (r) 3.0 (2006):

squashed
    adj 1: that has been violently compressed; "the squashed looking
           nakedness of the fledgling birds"

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "squashed":
   crushed, even, flat, flattened, flush, homaloidal, horizontal,
   level, plain, plane, quashed, quelled, repressed, rolled, smashed,
   smooth, smoothed out, smoothened, smothered, squashed flat,
   squelched, stifled, subdued, suffocated, suppressed, tabloid,
   tabular, trodden, trodden flat