If someone risks his career for a loved one, that would be letting it fly.
If someone takes a shortcut while driving by quickly going the opposite direction on a one wayroad when time is of the essence, that would be letting it fly.
A sexual act in which one person sticks their butt in the air in such a way so that their anus is exposed while another person sticks a BeyBlade in the first person's anus by the tip and then proceeds to spin or "let rip" the BeyBlade.
"How'd it go with Stacy last night?"
"Dude, we went back to her place and were totally letting it rip!"
Gina: "Are you going to wash that frying pan with the egg stuck on it?"
Chris: "No, I'm letting it soak. Are you going to rinse the cum off your tits?"
Gina: "No, I'm letting it soak."
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.