- 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.
adjectivedef·fer, def·fest Slang
Origin of defShort for definite.
(comparative deffer, superlative deffest)
- (US, slang) very good (short for "definitive" or "definitely")