Call a word or phrase pejorative if it is used as a disapproving expression or a term of abuse. Tree-hugger is a pejorative term for an environmentalist.
Coming from the Latin word for "worse," pejorative is both an adjective and a noun. As an adjective, it means disapproving or disparaging. Hack is a pejorative term for a bad writer. If you call someone a politician in the pejorative sense, you mean that they are scheming and out for personal gain. Terms of abuse such as jerk and negative euphemisms such as bottom feeder are pejoratives, words you use when you want to call someone a bad name.