a phrase used to describe and forewarn a girl who is giving you a blow job or hand job that you are about to cum. most often it is a phrase said just before "blast off" while receiving a blow job, however, it can also be used as ejaculation takes place if you want the girl to be somewhat suprised.
because the term is not very studly, it is not meant to be used to impress the girl, but just just to lighten the mood of a sexual encounter and make the sex more lighthearted, casual, or less romantic by adding some dumb comedy to things.
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.