birdie

Concise Oxford English Dictionary © 2008 Oxford University Press:
birdie/ˈbɜːdi/

▶noun (pl. birdies)

• 1 informal a child's word for a bird.

• 2 Golf a score of one stroke under par at a hole.

▶verb (birdies, birdying, birdied) Golf play (a hole) with a score of one stroke under par.

– origin C18: dimin. of bird; the golf term from US sl. bird, denoting something excellent.