A boilersuit is a loose fitting garment covering the whole body except for the head, hands and feet. The 1989 edition of the Oxford English Dictionary lists the word boilersuit first on 28 October 1928 in the Sunday Express newspaper. The garment is also known as coveralls in North America, or as an overall (or "overalls") elsewhere, especially in the UK; in North America "overall" is more usually understood as a bib-and-brace overall, which is a type of trousers with attached suspenders. A more tight-fitting garment that is otherwise similar to a boilersuit is usually called a jumpsuit. The "siren suit" favoured by Winston Churchill (but also worn by many others in the UK when air raids were a threat) during the Second World War was closely similar to a boilersuit.
A boilersuit is a one-piece garment with full-length sleeves and legs like a jumpsuit, but usually less tight-fitting. Its main feature is that it has no gap between jacket and trousers or between lapels, and no loose jacket tails. It often has a long thin pocket down the outside of the right thigh to hold long tools. It usually has a front fastening extending the whole length of the front of the body up to the throat, with no lapels. It may be fastened with buttons, a zip, velcro, or snap fasteners. Boilersuits with an attached hood are available. The word "boilersuit" may also refer to disposable garments such as DuPont's Tyvek suits.
Boilersuits are so called because they were first worn by men maintaining coal-fired boilers. To check for steam leaks or to clean accumulated soot from inside the firebox of a steam locomotive, someone had to climb inside, through the firehole (where the coal is shovelled in). A one-piece suit avoids the potential problem of loosened soot entering the lower half of one's clothing through the gap in the middle. As the firehole opening is only just large enough for a fit individual to negotiate, a one-piece suit also avoids the problem of the waistband snagging on the firehole as one bends to wriggle through, or of jacket tails snagging if one has to come out backwards.
Coveralls are most often worn as protective clothing over "street" clothes at work, but sometimes instead of ordinary jacket and trousers.
The French police unit Compagnies Républicaines de Sécurité use boilersuits as a uniform. Similar coveralls made of Nomex in olive drab (and more recently, desert tan) are also used by the crews of armoured fighting vehicles in the US Army and Marine Corps, where the men and also their suits are sometimes called "CVCs", an abbreviation of "Combat Vehicle Crewman". More form fitting coveralls with many zippered pockets, originally made of cotton treated for flame resistance, but made of Nomex since the late 1960s, have been used as flight suits since the beginning of World War II.
Coveralls called student boilersuits are used by university students in some Nordic countries as a sort of party-uniform, with insignia on the back and colour varying with programme and university.
For fans of the horror genre of film, the boiler suit is irrevocably associated with the slasher subgenre, being regularly worn by both Michael Myers of the Halloween films and by Jason Voorhees of the Friday the 13th franchise.
In 1919, the Italian designer Thayaht started designing his most famous piece, the TuTa, which he called "the most innovative, futuristic garment ever produced in the history of Italian fashion". It was an early example of what are now known as coveralls, intended to revolutionise fashion and create a modern and particularly Italian style. With help from his artist brother RAM (Ruggero Alfredo Michahelles) he launched the new design in 1920, and the pattern was published by the newspaper La Nazione so that the TuTa became accessible to all. Intended as a practical item of clothing for the everyday, it was instead adopted as a fad by high Florentine society.