Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines.

It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult.

The fuel can vaporize due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.

Vapor lock was far more common in older gasoline fuel systems incorporating a low-pressure mechanical fuel pump driven by the engine, located in the engine compartment and feeding a carburetor. Such pumps were typically located higher than the fuel tank, were directly heated by the engine and fed fuel directly to the float bowl inside the carburetor. Fuel was drawn under negative pressure from the feed line, increasing the risk of a vapor lock developing between the tank and pump. A vapor lock being drawn into the fuel pump could disrupt the fuel pressure long enough for the float chamber in the carburetor to partially or completely drain, causing fuel starvation in the engine. Even temporary disruption of fuel supply into the float chamber is not ideal; most carburetors are designed to run at a fixed level of fuel in the float bowl and reducing the level will reduce the fuel to air mixture delivered to the engine.

The word asshole, a variant of arsehole, which is still prevalent in British and Australian English, is a vulgar to describe the anus, often pejoratively used to refer to people.

The word arse in English derives from the Germanic root *arsaz, which originated from the Proto-Indo-European root *ors — meaning buttocks or backside. The combined form arsehole is first attested from 1500 in its literal use to refer to the anus. The metaphorical use of the word to refer to the worst place in a region, e.g., "the arsehole of the world") is first attested in print in 1865; the use to refer to a contemptible person is first attested in 1933. In the ninth chapter of his 1945 autobiography, Black Boy, Richard Wright quotes a snippet of verse that uses the term: "All these white folks dressed so fine / Their ass-holes smell just like mine ...". Its first appearance as an insult term in a newspaper indexed by Google News is in 1965. As with other vulgarities, these uses of the word may have been common in oral speech for some time before their first print appearances. By the 1970s, Hustler magazine featured people they did not like as "Asshole of the Month." In 1972, Jonathan Richman's Modern Lovers recorded his song "Pablo Picasso," which includes the line "Pablo Picasso was never called an asshole."