Sign up definition . to agree to become involved in an organized activity . to join a group or organization . Learn more..Define sign up phrasal verb and get synonyms. What is sign up phrasal verb ? sign up phrasal verb meaning, pronunciation and more by Macmillan Dictionary..Definition of sign up. intransitive verb. to sign one s name as to a contract in order to obtain, do, or join something sign up for insurance sign up for classes..Sign up definition If you sign up for an organization or if an organization signs you up , you sign a | Meaning, pronunciation, translations and examples..Definition of sign up in the Idioms Dictionary. sign up phrase. What does sign up expression mean? Definitions by the largest Idiom Dictionary..Define sign up. sign up synonyms, sign up pronunciation, sign up translation, English To change the ownership of property by means of a legal document ..Sign up meaning, definition, what is sign up to put your name on a list for something Learn more..Sign up definition, an act or instance of signing up. See more. a token indication. any object, action, event, pattern, etc., that conveys a meaning..