complain vs sound off

complain and sound off both are verbs.

Word	Noun	Adjective	Verb	Adverb
complain	No	No	Yes	No
sound off	No	No	Yes	No

As verbs, complain and sound off are synonyms defined as:

complain and sound off: express complaints, discontent, displeasure, or unhappiness

Other synonyms of complain include kick, kvetch, plain, quetch.

complain (verb)	sound off (verb)
express complaints, discontent, displeasure, or unhappiness	express complaints, discontent, displeasure, or unhappiness
make a formal accusation; bring a formal charge	express one's opinion openly and without fear or hesitation
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