(linguistics) A type of noun where the meaning of the form changes with respect to the context. E.g., 'Today's newspaper' is an indexical form since its referent will differ depending on the context. See also icon and symbol.
(economics) A single number calculated from an array of prices or of quantities.
(sciences) A number representing a property or ratio, a coefficient.
(Britain, Australia, automotive) A trafficator (dated definition); each of the flashing lights on each side of a vehicle which indicate a turn is being made to left or right, or a lane change etc.