In telecommunication, forward scatter is the deflection--by diffraction, nonhomogeneous refraction, or nonspecular reflection by particulate matter of dimensions that are large with respect to the wavelength in question but small with respect to the beam diameter--of a portion of an incident electromagnetic wave, in such a manner that the energy so deflected propagates in a direction that is within 90° of the direction of propagation of the incident wave.

The scattering process may be polarization-sensitive, i.e., incident waves that are identical in every respect but their polarization may be scattered differently.

Source: from Federal Standard 1037C