Green’s Dictionary of Slang

squash v.

1. to crush verbally.

[US]Eble Campus Sl. Apr. 5: squash – put an end to.
[US](con. 1990s) in J. Miller One of the Guys 86: ‘If they get into a scrap [...] we make ’em show love anyway. Just tell ’em to squash it’.

2. (US) to sort out a problem.

[US]Ersine Und. and Prison Sl.
[US]Goldin et al. DAUL 206/1: Squash, v. 1. To quash, as a criminal complaint or indictment.
[US]Bentley & Corbett Prison Sl. 16: squash To straighten out, to take care of or stop something.
[US]Source Aug. 47: I once found myself in a sticky situation where I had to try and squash beef for a client who was involved with a [gang] from the other side.

In phrases

get off the squash (v.)

(US) to have sexual intercourse.

[US]V.F. Nelson Prison Days and Nights 27: They want to get off the squash, so they fix it up with this white broad to take on the whole four of them.

In exclamations