signal

noun

1. Now Rare a token or indication
2. a sign or event fixed or understood as the occasion for prearranged combined action: a bugle signal to attack
3. anything which occasions a certain action or response
4. 1. a sign given by gesture, flashing light, etc. to convey a command, direction, warning, etc.
   2. an object or device, as a red flag, flashing light, etc., providing such a sign
5. in some card games, a bid or play designed to guide one's partner
6. in telegraphy, radio, television, etc., the electrical impulses, sound or picture elements, etc. transmitted or received
7. Football code words, numbers, etc. called out, esp. by the quarterback, to indicate which play or defense to use next

adjective

1. not average or ordinary; remarkable; notable
2. used as a signal or in signaling

transitive verb signaled or signalled, signaling or signalling

1. to make a signal or signals to
2. to make known or communicate (information) by signals

intransitive verb