harm a hair on someone's head

• harm a hair of someone's head

harm a hair on someone's head

1. (figuratively) To hurt someone.

   Synonym: touch a hair on someone's head

• Chiefly used in negative sentences, as an admonition: a person should not be hurt in the slightest degree, or else there will be consequences.

• “harm a hair on someone's head”, in Cambridge English Dictionary, Cambridge, Cambridgeshire: Cambridge University Press, 1999–present.
• “harm a hair on someone's head” in Longman Dictionary of Contemporary English, Longman.