I turn my back for half-a-freaking second and it's the future.
Wikipedia:
Zentai (from the Japanese ゼンタイ) is a common term for skin-tight garments that cover the entire body. The word is a contraction of zenshin taitsu (全身タイツ) ("full-body tights"). Zentai is most commonly made using nylon/spandex blends, but other materials such as cotton and wool are used as well.
Some companies have tried to create mainstream brands of the suits, by dropping the traditional name; in particular, examples include RootSuit in the United States and Morphsuit in the United Kingdom.