1. The cumulative process in which an electron or other charged particle accelerated by a strong electric field collides with and ionizes gas molecules, thereby releasing new electrons which in turn have more collisions, so that the discharge is thus self- maintained. Also known as avalanche effect; cascade; cumulative ionization; electron avalanche; Townsend avalanche; Townsend ionization.

2. Cumulative multiplication of carriers in a semiconductor as a result of avalanche breakdown. Also known as avalanche effect.

A mass of snow or ice moving rapidly down a mountain slope or cliff.