Three strokes under par on one hole — a 2 on a par-5, or a hole-in-one on a par-4. Americans also call it a double eagle. It's one of the rarest feats in golf, far rarer than an ace: it needs a huge drive and holing out a long second shot, with odds often quoted around one in a million. Gene Sarazen's albatross at the 1935 Masters — "the shot heard 'round the world" — is still the most famous one ever made.