on the fly adverb 3on-the-fly adjective 1 adverb3 •While in the air, without having touched the ground.Jones caught the ball on the fly. •Spontaneously or extemporaneously; done as one goes, or during another activity.The software program has a table of values for some results, but calculates others on the fly. •(slang) On the move.The Owl is flying high, frightening to the eye. The Rattler is nearby, Cool is on the fly. Danger is his business. — 1966 on-the-fly adjective1 •Performed on the fly.
