sign on

Verb

sign on (third-person singular simple present signs on, present participle signing on, simple past and past participle signed on)

1. To join something, after signing.
2. To commit oneself, as to a project, a goal, an organization, a cause.
   • I never signed on for this.
   • By January of 1996 President Clinton himself had apparently signed on with his declaration in the State of the Union message that "the era of big government is over."1997 September, Bernard A. Weisberger, “What made the government grow.”, in American Heritage, volume 48, number 5, page 34
3. To begin broadcasting a radio or television signal, usually at the beginning of a broadcasting day and after being off the air for several hours.
   • Years ago, the TV station would sign on at 5 a.m., but now it broadcasts 24 hours a day.
4. (idiomatic) To log on; to start using a computer, radio, or other multicast device; to start talking.
   • Edward ran a pale hand through his perfect golden-bronze hair, then signed on to 4chan.org, the darkest place on the Internet, where all his vampire compatriots spent their time.2009 June 1, Randall Munroe, “Troll Slayer”, in xkcd

   Synonyms:

   log in, log on, sign in

   Antonyms:

   log off, log out, sign off, sign out

5. (UK, intransitive) To apply to receive unemployment benefits.
   • Oh, one thing led to another; you know. I just sort of faffed around — I just did odd jobs; and sometimes in between I signed on.1999, Madeleine St John, chapter 28, in A Stairway to Paradise