From Longman Dictionary of Contemporary Englishlet fly (something)let fly (something)a)SHOUTto suddenly start shouting angrily at someoneSYN let looseThe prisoner let fly with a torrent of abuse.b)ATTACKto suddenly attack someone, especially with bullets or a weapon that is thrownlet fly (something) withThe soldiers let fly with a hail of machine-gun fire. →flyExamples from the Corpuslet fly (something)• He located running back John Fuqua 20 yards downfield and let fly.• Sit it on a hill and wait till the enemy is within half range and then let fly.• The Bashers tightenedlips, hunchedshoulders, and let fly.• You have only to come close enough to my hide and I let fly.• It seems that the Battler and Rico let fly at somebody who was coming out of the back door of the Regal Arms.• Kimberley let fly at the dangling men from a hopeless range.• And there all the time, a line of kneeling archers, letting fly from behind their rankedshields.• If the threat still persists, he will let fly with one or both hindlegs.