The term "ostrich" is used to describe the completion of a hole using five less strokes than the par. Each hole is assigned a number of hits that is considered to be par, otherwise known as average for the course. For example, a par five hole requires the golfer to sink the ball in the hole in five shot attempts to maintain a decent pace for the round. Since an ostrich refers to hitting five less shots than the par, the only way to score an ostrich is to hit a hole-in-one on a par six, or finish the hole in just two shots on a par seven. In other words, the golfer must place the ball in the hole on the very first shot attempt. It is for this reason that ostriches are very rare in golf. In fact, it is actually impossible to achieve an ostrich in professional tournaments, as the maximum par for any given hole on the pro tour is five strokes.
Since shooting an ostrich is extremely uncommon given that most holes do not have a large enough par to allow for it, experienced golfers generally do not concern themselves with the term. In fact, ostriches are considered to be golf folklore, with the name being derived from the fact that actual ostriches are a unique and rarely seen species.