The act of 'accidentally' forgetting an article of clothing or object to give yourself a reason to come back to someone's place and fuck.
When Jeremy left his hat at her house, she was convinced that it was a sexcuse article. This was proven a fact when he asked to come over to collect his hat because he wanted a bootycall.
While visiting my parents, Jeff and I usually use the sexcuse of needing a gallon of milk from the grocery store. That gets us out of the house long enough for a quicky in the backseat of the car.
A person of the rapey persuasion; somebody who hears "yes please" when everybody else hears "fuck off and don't touch me, you dirty dirty minger". Sex cases can come from all walks of life, but are united by the all consuming urge to sniff your discarded underwear, whilst fapping off to childhood memories of being emotionlessly beaten by their cold and distant father.
Yeah, I wouldn't go out with him, he's a right sex case. You know he's on the register for perving through the nursing home windows and wanking off?
That Josef Fritzl turned out to be a proper sex case, didn't he?