When a man or woman who are usually kept and well groomed suddenly goes on hiatus of personal appearance. The phrase itself comes from the Groucho Marx who infamously sported huge untamed eyebrows.

For men going with groucho is usually growing a beard, seize of all manscapping, and a newfound lingering odor.

For women its usually the stopping of any eyebrow plucking, leg shaving, waxing, makeup wearing, or hair brushing.

Literally everyone, ever. Including the writer of this definition.