compress
Part of Speech: verb
Definition: compact, condense
Synonyms: abbreviate, abridge, abstract, bind, boil down, coagulate, concentrate, consolidate, constrict, contract, cram, cramp, crowd, crush, decrease, dehydrate, densen, densify, epitomize, force into space, make brief, narrow, pack, press, press together, ram, reduce, restrict, shorten, shrink, shrivel, squash, squeeze, stuff, summarize, syncopate, telescope, tighten, wedge, wrap
Antonyms: blow up, expand, extend, fill, increase, loosen, stretch, uncompress, uncondense

squash
Part of Speech: verb
Definition: compress
Synonyms: annihilate, bear, bruise, crowd, crush, distort, extinguish, flatten, jam, kill, macerate, mash, pound, press, pulp, push, put down, quash, quell, scrunch, shut down, sit on, smash, squeeze, squish, stamp on, suppress, trample, triturate
Notes: quash means to crush or to subdue or to suppress or extinguish summarily and completely, while squash means to compress, crush, or squeeze
Antonyms: fan, open, uncompress

Main Entry: flatten
Part of Speech: verb
Definition: level out
Synonyms: abrade, beat down, compress, crush, debase, deflate, depress, even out, fell, floor, flush, grade, ground, iron out, knock down, lay, lay low, mow down, plane, plaster*, prostrate, raze, roll, smash, smooth, spread out, squash, straighten, subdue, trample
Antonyms: break, elevate, make uneven, raise, round
* = informal/non-formal usage