sign up phrasal verb ( see also ↑ sign )
1 . to put your name on a list for something because you want to take part in it
sign up for
I’m thinking of signing up for a yoga course.
sign up to do something
Over half the people who signed up to do engineering were women.
2 . sign somebody ↔ up if someone is signed up by an organization, they sign a contract in which they agree to work for that organization:
Several well-known researchers have been signed up for the project.