Letting the birds out

When a big assed girl (especially those named Susan) lets their fucking rangoon filled tits out for all to see. Done especially in swimming pools and at nude beaches.

Man: Oh fuck! Is she really gonna do it?!
Other man: She’s really gonna fucking do it! She’s letting the birds out!
Susan: Hey boys, want some rangoon loaded fuckers!?

Let the cows out

Inadvertently or otherwise telling something said in confidence; i.e. "letting the cat out of the bag," or "spilling the beans."

I can't believe you trusted her with your secret; she will always let the cows out!

Let the dog out

To burn one on your lunch break, getting high

Stephanie always says she is going to “let the dog out” when leaving for her lunch break.