someone's heart is in their mouth
US /ˈsʌm.wʌnz hɑːrt ɪz ɪn ðer maʊθ/
UK /ˈsʌm.wʌnz hɑːrt ɪz ɪn ðer maʊθ/

1.
심장이 입 밖으로 튀어나올 것 같다, 매우 긴장하다
to feel very nervous or frightened
:
•
When the roller coaster started, my heart was in my mouth.
롤러코스터가 시작되었을 때, 심장이 입 밖으로 튀어나올 것 같았다.
•
Her heart was in her mouth as she waited for the exam results.
시험 결과를 기다리는 동안 그녀의 심장은 입 밖으로 튀어나올 것 같았다.