Definition of you could have knocked me or her, him, etc. down with a feather in English:

you could have knocked me (or her, him, etc.) down with a feather

informal Used to express great surprise.
More example sentences
  • But when I read it, you could have knocked me down with a feather.
  • I felt sure it was something physical like a virus, so you could have knocked me down with a feather when he diagnosed depression.
See parent entry: knock

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Word of the day hypnopompic
Pronunciation: ˌhɪpnə(ʊ)ˈpɒmpɪk
adjective
relating to the state immediately preceding waking up