observer-- An individual charged with helping a referee in a golf match determine questions of fact and monitor rule violations.

obstruction-- An artificial object on a golf course from which relief may often be taken. Obstructions may be immovable or moveable.

Off-center-- A shot which does not strike contact the center of the club face typically resulting in a poor shot.

offset-- A club type where the head is set behind the club shaft.

one up -- In match play when a team or player leads by one hole.

one-iron-- An iron with very little loft that is typically difficult to hit. A 1-Iron typically hit's the ball 180 to 220 yards. May also be called a driving iron.

one-putt-- To hit the ball from its initial location on the green into the cup in one stroke.

one-wood-- Another name for a driver or one-metal.

open-- A golf tournament in which anyone can enter including professionals and amateurs.

open stance-- Body posture in which the left foot (for a right-handed golfer) is pulled away from parallel (backward) with the intended target line. An open stance can be used to produce a fade shot.

out-- The initial 9 holes on an 18 hole course.

out of bounds-- Designated area on or surrounding a golf course in which a ball is not allowed to be played. Hitting a ball out of bounds will incur a penalty.

overclub-- To incorrectly select and/or hit a club that will typically travel further than intended.

overlapping grip-- A type of golf grip(hand position) in which the pinkie of the right hand overlaps the area between the forefinger and the middle finger of the left hand (and vice-versa for a left handed golfer).