"order to test public opinionfly high ??? informal to have a high aim to prosper or flourishfly the coop ??? US Canadian informal to leave suddenlylet fly ??? informal to lose one's temper (with a person): she really let fly at him to shoot or throw (an object) n ( pl flies)Also called: fly front (often plural) a closure that conceals a zip, buttons, or other fastening, by having one side overlappi" . . . .