same as sign
Example: If they want to sign up the Manor for another series of weekends, we'll make it a condition that the resident authors are orphans.
to agree to do something, or to join a course or organization
Example: She’s decided to sign up for evening classes.
to put someone’s name on an official list for something
Example: Then he said, `Aye well, when they started talking about it, back in August, at first I thought I'd sign up for the army.
enlistjoinregistervolunteer