trebly adverb 2adjective 1forms 4 adverb2 •To three times the extent or degree; triply.For my part, I must do my best to save this fellow's trebly worthless life; Jim, you get me a basin. — 1883 •(no longer used) Three times, thrice adjective1 •Having treble, or high-pitched, qualities.With the room so bare, Ivret’s voice sounded different, trebly echoes ringing off her sibilants. — 2024 formsmore trebly · treblier · most trebly · trebliest