Multipath

In telecommunication, multipath is the propagation phenomenon that results in radio signals' reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting[?], ionospheric reflection and refraction, and reflection from terrestrial objects, such as mountains and buildings.

The effects of multipath include constructive and destructive interference, and phase shifting of the signal. In facsimile and television transmission, multipath causes jitter and ghosting.

Source: from Federal Standard 1037C and from MIL-STD-188