- The definition of def is a slang term that is excellent or first-rate.
An example of def used as an adjective is in the phrase "that music is def," which means the music is excellent.
Slang excellent; first-rate
adjectivedef·fer, def·fest Slang
Origin of defShort for definite.
(comparative deffer, superlative deffest)
- (US, slang) very good (short for "definitive" or "definitely")