MULLIGAN
Most simply put, a "do-over." Hit a bad shot? Take a mulligan and hit it again. Mulligans are played only when expressly agreed upon by all partners in a friendly match, and are never allowed when the official rules are being followed (i.e., in a tournament or handicap round). Mulligans are most commonly played on the first tee, or played as one mulligan per nine holes. Mulligans are often sold at charity tournaments (as distinguished from official tournaments) - for example, if you would like to have five mulligans to use during a round, you would pay to purchase them. Then, five times during a round when you wanted to hit a shot over, you would be able to do so.
The usage issue here is with its usage on the course. Most golfers use mulligans too freely and use them in competitive or official rounds when they are not allowed.