To move backward or away; withdraw or retire:
To agree or consent quietly without protest, but without enthusiasm
Or (intransitive) To enter or put forward for approval, consideration, marking etc.
To produce a return for effort or investment:
Succumb is defined as to give in to someone or something or to die.
Find another word for knuckle-under. In this page you can discover 8 synonyms, antonyms, idiomatic expressions, and related words for knuckle-under, like: retreat, give in, give up, acquiesce, submit, yield, succumb and buckle-under.