1) Discharge 2) Electric arc 3) Electric discharge 4) Spark 
A flashover is the near-simultaneous ignition of most of the directly exposed combustible material in an enclosed area. When certain organic materials are heated, they undergo thermal decomposition and release flammable gases. Flashover occurs when the majority of the exposed surfaces in a space are heated to their autoignition temperature and emi...
simultaneous ignition of combustible materials in a closed space, as when materials simultaneously reach their fire point; may also result in rollover.
a breakdown between electrodes in a gas or a liquid or in vacuum, at least partly along the surface of solid insulationdisruptive discharge external to the insulator, and over its surface, connecting those parts which normally have the operating voltage between thema short-circuit caused by arcing between brushes or brush-holders at the surface of the commutator of an electrical machine or from any of these parts to the frame
[n] - an unintended electric discharge (as over or around an insulator)
An unintended electrical discharge to ground or another phase. Flashovers can occur between two conductors, across insulators to ground or equipment bushings to ground.
An arc discharge through air around or over the surface of insulating materials, between parts at different potential or voltage. See Arc discharge
a disruptive discharge around or over the surface of a solid or liquid insulator. · the moment of conflagration or complete incineration caused by superheated air or combustibles.