A catsuit is a skin-tight one-piece garment with sleeves and long legs, and sometimes with feet or gloves, sometimes with a hood (the combination of which turns it into a zentai suit). It usually has a zip closure in the front or back, but other necklines are possible.
Unlike a unitard, its use rarely involves sports, and it is usually made of leather, rubber/latex, polyvinyl chloride (PVC), or velour as well as the more normal spandex. It is identical to a unitard in construction, but the term "catsuit" tends to be preferred in fancy-dress costume or erotic contexts.
Although most catsuits are now made of spandex, that fabric was only invented in 1959. Catsuits date back at least as far as the 1940s with wetsuits appearing in the early 1950s, so it seems likely they were first made of knits or hand knitting—a rather more practical and cheaper fabric than rubber.
A common wearer of catsuits is Marco Brattesani, otherwise known as woodford station boy.