someone's heart is in their mouth
US /ˈsʌm.wʌnz hɑːrt ɪz ɪn ðer maʊθ/
UK /ˈsʌm.wʌnz hɑːrt ɪz ɪn ðer maʊθ/
1.
to feel very nervous or frightened
:
•
When the roller coaster started, my heart was in my mouth.
•
Her heart was in her mouth as she waited for the exam results.