| Noncoincidence (n.) Lack of coincidence. |
| quarterback / signal caller / field general (American football) the position of the football player in the backfield who directs the offensive play of his team, "quarterback is the most important position on the team" |
| alarm / warning device / alarm system a device that signals the occurrence of some undesirable event |
| alarm clock / alarm a clock that wakes a sleeper at some preset time |
| burglar alarm a warning device that is tripped off by the occurrence of a burglary |
| fire alarm / smoke alarm an alarm that is tripped off by fire or smoke |
| signal box / signal tower a building from which signals are sent to control the movements of railway trains |
| signal level the amplitude level of the desired signal |
| signal detection / detection the detection that a signal is being received |
| signal / signaling / sign any nonverbal action or gesture that encodes a message, "signals from the boat suddenly stopped" |
| starting signal / start a signal to begin (as in a race), "the starting signal was a green light", "the runners awaited the start" |