Coverall is also known as boilersuit

A boilersuit is a loose fitting garment covering the whole body except for the head, hands and feet. The garment is also known as coverall 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.

Description
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, velco, or snap fasteners. Boilersuits with an attached hood are available.

Boilersuits are so called because they were first worn by men maintaining coal -fired boilders. 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.^{[original research?]}

Usage

Coveralls are most often worn as protective clothing over "street" clothes at work, but sometimes instead of ordinary jacket and trousers.