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"