Definition of "sign on" [sign on]

• The time of day when a radio or television station begins broadcasting, usually after being off the air for several hours. (noun)
• To join something, after signing. (verb)
• To commit oneself, as to a project, a goal, on organization, a cause. (verb)
• 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. (verb)
• To log on; to start using a computer, radio, etc., or to start talking. (verb)

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• "The sign on the box read: “Malcolm's Poultry Farm,100baby chickens.”"
• "Rather, I added her to my buddy list, watched her flickering presence sign on and off, and hit REFRESH on her diary at least five times a day."
• "There they found countless abandoned rifles and cannons as well as a dungeon containing a half-crazed woman with a wooden leg and a long, black trench coat, plus a tent with a sign on it that said DO NOT DISTURB in French."