(rail transport) A signal set at danger and showing a red light or other stop indication, which a train driver must not pass until it changes or until manually cleared past the signal by a dispatcher.

(economics) A sign, attached to a commodity and concerning its price, that is intended to increase demand for it

(biology) A biochemical sequence in which one molecule that receives a signal activates another molecule

plural of signal pistol

A handgun designed to discharge an illumination flare.

(rail transport) a structure erected over one or more railway tracks, carrying one or more signals. Smaller structures usually have a single support, and larger structures are supported on both sides.

plural of signal gantry

Alternative spelling of danger signal.

plural of signalling pathway

plural of semaphore signal