certain defeat; inevitable loss
A somewhat formal or literary noun meaning a situation where defeat is unavoidable. Often used in analytical or dramatic contexts, such as war, sports, or competition.
We entered this battle prepared for certain defeat.
彼は必敗の試合でも最後まで諦めなかった。
Even in a match where defeat was certain, he didn't give up until the end.
必敗 means 'certain defeat', the direct opposite of 必勝's 'certain victory'.
Compound of 必 (certain, inevitable) and 敗 (defeat). The reading ひっぱい follows the standard on'yomi of the characters.