interceptor

Anything that intercepts something else.
A fast, maneuverable fighter aircraft designed to intercept and destroy enemy aircraft before they can attack.
A guided missile designed to intercept and destroy enemy missiles.
(architecture) A device to trap, remove, or separate deleterious, hazardous, or undesirable matter (such as oil, grease, gasoline, sand, and sediment) from normal waste conveyed through it, permitting normal sewage or liquid wastes to discharge into the disposal terminal by gravity.
(computing) A hook routine that intercepts normal program flow to carry out a task.
a sewer which intercepts sewerage destined for an outfall (e.g. into a river) and redirects it to sewerage treatment plant