My foot!

my foot

An exclamation of disdain or disagreement. Busy my foot! I know he's lying just to get out of this commitment he made.
See also: foot
Farlex Dictionary of Idioms.

My foot!

Inf. I do not believe it!; Like hell! (An exclamation of contradiction.) Your prices are the best in town, my foot! I know two places cheaper. She's going to marry you? My foot!
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

my foot!

used to express strong contradiction or disbelief. informal
Farlex Partner Idioms Dictionary

...my ˈfoot!

(informal, humorous) a strong way of saying that you disagree completely with what has just been said: ‘Ian can’t come because he’s tired.’ ‘Tired my foot! Lazy more like!’
Farlex Partner Idioms Dictionary

My foot!

exclam. I do not believe it!; Like hell! (An exclamation of contradiction.) You’re the best in town, my foot!
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • my foot
  • fleet of foot
  • foot it
  • be hand and foot to (one)
  • on foot
  • foot up
  • shoot oneself in the foot, to
  • foot
  • set foot in
  • set foot in (some place)