Something that
intercepts. Seriously, this term is typically used to refer to a warplane designed to intercept (and destroy) incoming threats - an
air defense fighter. Typically, the incoming threat is a
bomber or
cruise missile.
The film Mad Max pictured a dystopic future Australia where the highway police employed special cars and drivers to deal with high-speed felons. These were called Interceptors.
Aircraft so designated are typically quite fast and emphasize air-to-air armaments. Their speed allows them to engage enemy threats as far out from their targets as possible.