Lightning is a huge electrical discharge common in violent weather. It was often represented in period art as “fire from heaven”. In Society heraldry, lightning is represented as “flashes” and “bolts”. The distinction is made in blazonry to denote two different styles of emblazonry, one of which was common in early Society armory but is no longer permitted.
A “lightning flash” is a tapering bevilled stripe, found in modern comic books; for that reason, it’s sometimes termed (only half-jokingly) a “shazam”. As a purely modern depiction, this form is no longer permitted in Society heraldry.
A “lightning bolt” is an embattled stripe with barbs at either end. The depiction is period: two lightning bolts in saltire are found in the standard emblazon of the thunderbolt [de Bara 128]. This form is still permitted in Society heraldry, though it’s considered a step from period practice when not used as part of a thunderbolt. As it has no default, the orientation must be explicitly blazoned; the illustration shows both forms of lightning palewise.
Japanese Mon represent lightning (inazuma) in a distinctive stylization, as borne by Yamashina [Hawley 75], but this has not yet been dated to period.
Algarth of Mount Coruscation bears: Per chevron azure and gules, two lightning flashes in pile argent.
Rosaline Weaver bears: Argent, a lightning bolt palewise azure.
Phillip of Ghent bears as a badge: Sable, issuant from a single strand, double spiral Japanese lightning flash lozengewise, in chief and in base two scarpes argent.