A costume that makes the wearer look like an anthropomorphic tomato. Typically red and has a hood with a green "stem" on top.
Most commonly seen worn by Toshinou Kyouko from Yuru Yuri; the pixiv tag used for it (トメィトゥ, "tomeitou") is based on the way she pronounces the word in the manga. (The vegetable's name is normally トマト in Japanese, pronounced "tomahtoh".)