whole nother thing

whole other thing

Something very different to, and often more difficult or complicated than, something else. Often spoken or written more colloquially as "whole 'nother thing." I don't know what you think you know from working in television, but working on a film is a whole other thing! It's one thing to babysit your friends' kids from time to time, but having your own children is a whole 'nother thing.
See also: other, thing, whole
Farlex Dictionary of Idioms.

whole nother thing

Rur. a completely different matter. (Often "corrected" to a whole other thing. The word nother is a shortening of another.) Borrowing! That's a whole nother thing! I thought you said stealing!
See also: nother, thing, whole
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • whole other thing
  • garnish
  • garnish with
  • garnish with (something)
  • be in the market for
  • find (oneself) in the market for (something)
  • make a go of
  • make a go of (something)
  • make a go of something
  • cough it up