This word is a contraction of "Cupid Stunt", who was a character on the Kenny Everett Show in the 1980s. This in turn is a spoonerism of "Stupid Cunt". The expression is used by people who watched TV in the 1980s, usually to describe people who were born after show's popularity waned and are therefore unfamiliar with the expression.
1: That fellow was playing chicken with the trains on the railway line.
2: What a cupid.
A mascot created to represent a website, similar to how restaurants have mascots. Site-Tans often embody the theme, purpose, or personality of the website they represent, making them a memorable part of the website. (Example: Rule34, e621, etc.)
Spending your time and money for your own improvement, future success or good time / enjoyment. As opposed to spending your money and / or time trying to please people especially people you don't like.
" I can't believe it! I just blew her rent money hosting a big dinner party for my frenemies."
"Yeah it sounds like you don't know how to invest in yourself. "