Idiomatic expression meaning that a secret has been revealed, usually unintentionally, similar to the expression "to spill the beans." Can also be expressed as "the cat is out of the bag."
Bobby let the cat out of the bag when he accidentally mentioned to Amanda the surprise birthday party they were planning on throwing for her.
When a woman doesn't wear any underwear, especially if her pussy is somehow exposed while not wearing underwear. You cannot call it going Commando like when a man doesn't wear underwear. It's called that because your dick is somewhat exposed to the elements.
"Dude, when the wind just blew a minute ago this hotties dress went up high and she wasn't wearing any underwear...Cat's out of the Bag!!"
A trip to a grocery store, convenience store, or gas station for the sole purpose of buying an excessive amount of junk food and sugary drinks, usually with friends. A chud run often happens late at night and ends with everyone involved hating themselves afterwards.