Other forms: grinches
A grinch is a person who's so cranky and mean-spirited that they want to ruin everyone else's fun. If you keep being such a grinch, your friends will start to avoid you!
Dr. Seuss didn't coin grinch when he wrote How the Grinch Stole Christmas, but he is credited with turning it into a familiar, everyday word. Before the book was published in 1957, other unpleasant literary characters had the name Grinch, and the verb grinching was used to mean "a harsh, grating noise." Describing someone as a grinch today means they're a killjoy or party pooper, trying to make everyone feel as bad as they do.