A potatis is a swedish word, meaning that you are completely useless. Originally the word translated to potatoe in English, but that meaning has been lost.
You are such a potatis, failing to throw a granade properly without killing your friends.
Adj. Joking term to describe ones self or others as round, funny looking, or potato shaped. Can also be used as a flirtatious term for someone you like, usually when you are trapped in the friend zone.
Boy: What do you think of yourself? Beautiful, sexy, smart?
Girl: Potatoish
Boy: Potatoish? Thats okay, i like potatos.