A phonetic spelling of the letter f (normally spelled ef), the initial letter of the vulgar term fuck. Compare pee.
Alternative forms 
eff (third-person singular simple present effs, present participle effing, simple past and past participle effed)
- (euphemistic, slang) Fuck.
- Eff off!
- And he kept saying, "Effing this, effing that."
Usage notes 
Eff is used to replace fuck as a taboo swearword but not in its sense of "to copulate".
Derived terms 
eff n (genitive singular effs, plural eff)
- The name of the Latin script letter F/f.