an extreme variation of the "coinslot", where a girl's pants ride so low that the amount of ass crack showing more closely resembles something into which one would jam a debit card.
Games (or otherwise) that involve the use of playing cards. See: balatro, poker, etc.
Can be used sincerely or jokingly, similar to "friendslop" and other -slop genres.
"Cardslop is the means by which all is revealed." -makoto "the persona" yuki, probably