[from the operation that removes the top of a stack, and the fact that procedure return addresses are usually saved on the stack] (also capitalized ‘POP’)

1. vt. To remove something from a stack. If a person says he/she has popped something from his stack, that means he/she has finally finished working on it and can now remove it from the list of things hanging overhead.

2. When a discussion gets to a level of detail so deep that the main point of the discussion is being lost, someone will shout “Pop!”, meaning “Get back up to a higher level!” The shout is frequently accompanied by an upthrust arm with a finger pointing to the ceiling.

3. [all-caps, as ‘POP’] Point of Presence, a bank of dial-in lines allowing customers to make (local) calls into an ISP. This is borderline techspeak.