Using a port scanner to find vulnerable computer systems.
"I was war dialing the school's network and found a backdoor, so I gave myself strait A's."
War dialing is scanning a range of telephones (ex. 555-555-xxxx) to find all sorts of stuff, like fax machines, carriers, and BBSes (remember this was a loooong time ago)!
Joe: Hey, I was war dialing our area code and found a hacking BBS!
Bob: Sweet! What's the number?