Idiom
let fly with somethinglet fly (with) (something)
1.
to throw something or shoot something from a weapon.
Police officers let fly canisters of tear gas.The guy in the leather jacket was leaping over the counter when I let fly with a soda bottle.
2.
to express yourself in a way that will excite or anger others.
If you disagree with the officials, it's bad form to let fly with four-letter words.When she got together with her friends, they would let fly all their innermost secrets.
Etymology: based on the idea of shooting an arrow