1. Putting yourself or someone else on a list for an activity, class, etc.
2. When someone is instant messaging you and they suddenly sign off because of something you say (similar to "hang up" on the phone)
Synonyms for sign up
On this page, you will find 30 slang terms related to sign up. Some of the top words include: P.O.S., bl, sms, IM, skizy, and 25 more.