def

UK: /dɛf/ US: /dɛf/ ,(def )

WordReference Random House Learner's Dictionary of American English © 2026

def² /dɛf/  adj. 

1. [Slang.] excellent:
   That hip-hop record is def!

WordReference Random House Unabridged Dictionary of American English © 2026

def  (def ), adv. [Informal.]

1. Informal Terms definitely:
   Going to Europe this summer? But def!

• by shortening

def¹  (def), adj. 

1. Slang Terms excellent:
   That hip-hop record is def!

• of uncertain origin, originally 1980–85, American.

def., 

1. defective.
2. defendant.
3. defense.
4. deferred.
5. defined.
6. definite.
7. definition.

Collins Concise English Dictionary © HarperCollins Publishers::

def / dɛf/ adjective

1. very good, esp of hip-hop

Etymology: 20th Century: perhaps from definitive

Collins Concise English Dictionary © HarperCollins Publishers::

def. abbreviation

1. definition