signal
noun
anything that serves to indicate, warn, direct, command, or the like, such as a light, a gesture, an act, etc.: a signal to leave.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
How come you so unsignalled, When I have watched so well?
From Ballads of Lost Haven A Book of the Sea by Bliss Carman