A person with the ability to hit another with their scrotum without the other's notice. Usually done by people who have had little to no sexual intercourse in at least four years.
Man did you see that? When the woman wasn't looking, Roberto opened his pants and gently struck her leg with his testicles. What a Knack Sacker.
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.