on the fly

• on-the-fly (adjective)

• Audio (General Australian):

  (file)

on the fly (not comparable)

1. (baseball, of the ball) While in the air, without having touched the ground.

   Synonym: in flight

   Jones caught the ball on the fly.

2. (idiomatic) Spontaneously or extemporaneously; done as one goes, or during another activity.

   Synonyms: in flight, on the wing; on the spot; on the hoof (Britain)

   Hypernym: dynamically

   The software program has a table of values for some results, but calculates others on the fly.

3. (slang) On the move.
   • 1966, “Cool McCool (theme song)”, Bernie Green (music) (Cool McCool (television series)), performed by Bob McFadden:

     The Owl is flying high, frightening to the eye.
     The Rattler is nearby, Cool is on the fly.
     Danger is his business.

• OTFE, on-the-fly encryption