fall flat on your face

US /fɔl flæt ɑn jʊər feɪs/
UK /fɔl flæt ɑn jʊər feɪs/
"fall flat on your face" picture
1.

完全に失敗する, 面目を失う

to fail completely or to be unsuccessful in an embarrassing way

:
His grand plan to impress the boss fell flat on its face.
上司を感動させる彼の壮大な計画は完全に失敗した
The comedian's new jokes fell flat on their face with the audience.
コメディアンの新しいジョークは観客に全く受けなかった