def 1
/def/ , adv. Informal.
definitely: Going to Europe this summer? But def!
[ by shortening ]
def 2
/def/ , adj.
Slang. excellent: That hip-hop record is def!
[ 1980-85, Amer. ; of uncert. orig. ]
DEF
Meaning of DEF in English
Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012