Trisexual

A trisexual is a person who always tries to get sex but doesn't get it. They are overly eager or desperate and frequently fail in their attempts. The term "trisexual" humorously suggests that they will "try" anything in their pursuit of sex, yet despite their efforts, they rarely succeed. This word plays on the prefix "tri-," meaning "three," to imply the repeated nature of their attempts.

"John is so thirsty that he keeps hitting on every girl at the party but never gets anywhere. His charm doesn't work! Everyone knows him as the quintessential trisexual."