Definition of "what for" in English

Adverb

1. For what purpose.

   • What is this tool for?
   • That's what friends are for.

2. For what reason; why.

   • He wants four copies of it? What for?
   • Ow! What did you do that for?
   • What do you want to know for?

Noun

1. An unspecified punishment or rebuke.

   • When your dad gets home, he'll give you (a) what for.