“Cutting a rusty,” used particularly in the U.S. South and South Midlands, refers to doing something mildly outrageous like shouting a naughty word or pulling a prank. It’s likely related to the word restive, as in restive sleep, wherein someone’s tossing and turning, and an old sense of rusty applied to horses to mean “hard to control or stubborn.” This is part of a complete episode.