[sahyn-on, -awn]
  1. Radio and Television. the opening salutation, station identification, etc., at the beginning of the broadcast day.
  2. an act or instance of signing on.

Origin of sign-on

First recorded in 1880–85; noun use of verb phrase sign on Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for sign-on

Historical Examples of sign-on