1 suppress, subdue, put down, quell, quash, defeat, overcome, outdo, humiliate, Colloq shoot or slap down, take down a peg (or two), take the wind out of (someone's) sails, settle (someone's) hash:
The slightest sign of disapproval from No‰l was enough to squelch the most arrogant toady.
2 riposte, retort, comeback, quip, sally, gibe or jibe, barb, Colloq wisecrack, put-down:
One of the best squelches was when Oscar Wilde said, referring to a bon mot, 'I wish I'd said that', to which Whistler said, 'You will, Oscar. You will.'