Godan verb with 'ru' ending, Intransitive verb
to be completely weakened; to be utterly exhausted; to be worn out
彼は弱りきっていて、食欲がなかった。He was weak as a rat, and had no appetite. to be completely at a loss; to be at one's wits' end; to be greatly annoyed (by); to be fed up (with)
Also written 弱り切る【よわりきる】