1A convenient excuse or pretext put forward to hide one's real reason for doing, or not doing, something.
彼は忙しいという口実で誘いを断った。
He turned down the invitation with the excuse that he was busy.
出張を口実に実家に立ち寄った。
He used the business trip as a pretext to stop by his parents' house.
そんな見え透いた口実は通用しない。
Such a transparent excuse won't work.
何か口実を見つけて早退した。
I found some excuse and left work early.