Impact: Moment when the club strikes the ball.
Impediment: Loose debris that you can remove from around your ball as long as the ball doesn’t move.
Impregnable Quadrilateral: The Grand Slam.
Improve Your Lie: To move the ball to make a shot easier. This is illegal unless local rules dictate otherwise.
In Play: Within the confines of the course (not out-of-bounds).
Into Out: Swing path whereby the clubhead moves across the ball-target line from left to right.
In Your Pocket: After you’ve picked up the ball! (Generally after you finish a hole without holing out.)
Insert: Plate in the face of wooden clubs.
Inside Out: Clubhead moves through the impact area on a line to the right of the target. Most tour players do this. (See also outside in.)
Inside: Area on your side of a line drawn from the ball to the target.
Intended Line: The path on which you imagine the ball flying from club to target.
Interlocking: Type of grip where the little finger of the right hand is entwined with the index finger of the left.
Investment Cast: Clubs made from a mold.