Are you feeling cranky or irritable and complaining about every little thing that annoys you? You're grouchy.
Someone who's grouchy is easily irritated, like the grouchy bus driver who yells for everyone to sit down and be quiet, or your grouchy brother, who grumbles about what's being served for dinner — or the notoriously grouchy Oscar the Grouch from "Sesame Street." Grouchy was college slang in the late 1800s, along with expressions like "to have a grouch on." The root might be grutch, "to complain or find fault with."