refers to the ignition cap at the base of a cartridge for a firearm. "bust a cap" means break the cap by pulling the trigger, setting off the explosion that propels the bullet
A slang term commonly used by members of Gen-Z to say that something is a lie. Similar to its variation “capping”, which is used to direct at another person who is a liar.
Person 1: Mom! Nick ate my ice cream!
Nick: That’s cap!
Variated:
Teacher: Jack, are you sure your dog ate your homework?
Jack: Yes!
Bob: You’re capping, Jack! I saw you throw it in the recycling bin yesterday!