The term ‘low amateur’ is used in the context of a professional golf tournament and refers to the amateur golfer with the lowest score.
Put simply, the term is simply another way to note the highest placed amateur golfer in a professional tournament such as The Masters.
These amateur golfers will be prohibited from being awarded, or accepting, any money or any type of financial award in golf so being awarded ‘low amateur’ is about as close as they will get.
Without a financial award, they are typically given a prize which can be different depending on the tournament.