What is a synonym for the word decline?

Answer 1

As a verb decline has these meanings:

TURN DOWN, synonyms = reject, brush aside, refuse, rebuff, spurn, repulse, dismiss; forgo, deny oneself, pass up; abstain from, say no; informal give the thumbs down to, give something a miss, give someone the brush-off; Brit. informal knock back.

DECREASE, synonyms = reduce, lessen, diminish, dwindle, contract, shrink, fall off, tail off; drop, fall, go down, slump, plummet; informal nosedive, take a header, crash.

DETERIORATE, synonyms = degenerate, decay, crumble, collapse, slump, slip, slide, go downhill, worsen; weaken, wane, ebb;

Answer 2

A synonym for decline is decrease.