From The Collaborative International Dictionary of English v.0.48 [gcide]:
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]
From WordNet (r) 3.0 (2006) [wn]:
squashed
adj 1: that has been violently compressed; "the squashed looking
nakedness of the fledgling birds"