Plastic explosives are a trap in Fallout.
Plastic explosives is a generic term referring to a brick of high explosive material which can be hand-molded into any shape. Primarily used by engineers, both civilian and military, for applications requiring precision and measured blasting, after the nuclear holocaust various brands of plastic explosives became used as tools and weapons. They are a fairly rare sight, at least compared to good old dynamite, its brother also invented by Alfred Nobel in the 19th century.
The primary commercial brand of plastic explosives encountered in the wasteland is the white Cordex, fitted with an electrical detonator and a timer.
A more powerful variant of dynamite, with a larger blast radius and power. This is generally meaningless, as it's hard to use as a weapon and dynamite knocks doors down just as good. However, it can be used for assassinations more efficiently.