A birdie.
One under par on a hole is called a "birdie".
It is called a double eagle or a hole in one.
Every hole has a par rating - usually 3, 4 or 5. One under means one less than this. So on a par 4 hole a score of 3 is one under par. This is called a birdie.
A birdie is one stroke under par on a given hole.
A birdie is a hole played one stroke under par.
A Three Under Par is either an Albatross or a Hole In One.
Birdie: one under par for that hole e.g. 3 on a par 4 Bogey: one over the par for that hole e.g. 5 on a par 4 eagle: two under the par for that hole e.g 3 on a par 5 or 2 on a par 4
For a round of golf- one under. For a given hole- a birdie.
Three under par on one hole of golf is an albatross or a double eagle.
One under par for a hole is one shot less than par, say you make a 3 on a par 4, this is a birdie. One under for a round is where you had a round which was one shot less than par, say you shot 71 on a par 72.For holes played, or for that round, or for the tournament, the player has taken one less shot to play those holes than par.
Each hole at golf has a standard number of strokes (number of times the ball is hit) to get it in the hole. This number is called Par, taken from the par value of stock. For example, if the standard number of strokes for a hole is four, it is called a Par four hole. If a player gets the ball in the hole in one less than (one under) Par, it is called a Birdie. Legend has it that a famous player's ball hit a bird in mid-air and he then completed the hole in one stroke under and the term Birdie was born. Making the hole in two strokes under Par is a larger bird so it's called an Eagle. Three strokes under Par an Albatross, because an Albatross is such a rare bird. If you take one more stroke than Par it's call a Bogey, after the Bogey Man. Two strokes over is a Double-Bogey. Three is a Triple-Bogey.
It is called a condor, 4 under par on one hole, very rare if not impossible.