Jail
Help, I'm in jail! Stated when you are faced with a very difficult shot.
Jerk
To hit the ball from a bad lie, rough or sand, with a downward cutting motion causing the clubhead to dig into the ground beneath the ball.
Jigger
An iron with moderate loft and a short shaft. No longer in use. Present equivalent is the 4 iron.
Jungle
A slang term for heavy rough.