Definition, synonyms and related words
Abbreviation of deficit.
"The truck driver had to stop at a rest area to refill his DEF tank before continuing the long haul."
Abbreviation of diesel exhaust fluid.
In plain English: Def is slang for a person who is very good at something, especially in sports or video games.
"She told him to stop being such def and listen to her."
Usage: Use "DEF" only to refer to diesel exhaust fluid used in vehicle emission systems; do not use it as slang for excellent or cool. This abbreviation is specific to industrial and automotive contexts involving selective catalytic reduction technology.
excellent; very good
"The def of that new playlist is perfect for a summer road trip."
In plain English: Def means something is really cool, awesome, or very good.
"The def game plan helped us win the match easily."
Usage: Use "def" only in informal spoken contexts to mean something is excellent or very good, such as calling a movie "def." Avoid using this slang abbreviation in formal writing or professional communications.
Abbreviation of definitely.
"Def, I'll be there for the meeting at two o'clock."
In plain English: Def means for sure or definitely, used to show you are completely certain about something.
"The new phone is def the best I've ever owned."
Usage: Use "def" informally in casual speech or text messages to emphasize that something is absolutely true, functioning as a shortened version of definitely. Avoid using this abbreviation in formal writing, academic papers, or professional correspondence where standard English is required.
The slang term def is a clipped form of the words definitive or definitely that entered English as informal shorthand. It also emerged as a stylized spelling of death used to express something being absolute.