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

plural of signal gantry

(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.

A handgun designed to discharge an illumination flare.

plural of signal pistol

plural of signal indication

plural of signal aspect

(historical) A kind of mechanical signal used on early American railroads, consisting of wooden balls, painted various colors, that were hoisted up and down a pole using a rope and pulley.

plural of signalling event

a signal, which can vary in strength due to various factors, transmitted and received by radio by means of radio waves.