A flyboy is a man who flies a plane — most often a military pilot, and most often in American talk. It is informal, and a bit old-fashioned: the kind of word you hear in war films, or from someone teasing a pilot. It can sound fond, or a little mocking, as if the speaker thinks pilots are showy.

It is not the formal job title. In the forces you would say pilot, aviator, or airman. You would not write flyboy on a form. It almost always means a man.

Though actually, there is a matching flygirl in some slang, but it is less common and does not always mean a woman pilot — so do not treat them as a neat pair. If you need a serious word, say pilot.