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)
guy1: i heard this year mr. herbert is teaching woodshop.
guy2: i have to go sign up for that class!

girl1: what happened last night? you totally signed up on me!
guy3: sorry, my internet connection is horrible.
by gimmieyertots March 22, 2005
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When there is an activity you are forced to do or did not want to do, you would say, "that is a sign up" because you didn't sign for the activity you are being forced to do
My mom told me to clean the poop out of the toilet, thats a sign up.
by Jett Hiu February 9, 2017
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This is a term used by pornhub it is basically for any of the ads on the top of the videos saying that you don’t have to sign up to go on this other website and ... it’s not bullshit
“Horny moms in your area no sign up no bullshit
“Wow I’m convinced... wait mom! Why are you the first one on this site!!”
by That1guy64 July 31, 2019
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When something is not what you agreed to or anticipated to be.
Why is my rent 2x higher now? I didn't sign up for this!
by bruhthisismyhandle September 12, 2021
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A universal saying for not getting what one wants, usually said by a cowardice.
(after moving in with a new roommate)

D: I want a new roommate not a third boyfriend! I didn't sign up for this!

Jack: Okay chill out queer-bait.
by Rex Kwon Do Dojo December 7, 2010
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