a person you now hate
a person who you dont want to have sex with anyone else
a person who you have sex with once in a while
a person who owes you child support
2) Your current bf/gf's ex. AKA an evil being that must be destroyed, at all costs. If you're a girl- for some reason, your bf's ex always seems to be a blonde with big boobs and a shitty personality who for some reason, makes you feel fat. If you're a guy- somehow, your gf's ex is famous among every girl you know, and if you ever bring him up, they can't stop telling you how "funny" and "amazing" he is. You also can't stop yourself from wondering if his equipment's bigger than yours.
My ex and I broke up after dating for two years because he/she had to move. We got along really well during those first two years, so we still keep in touch.
2) (After current gf meets ex gf)
Gf: "Well... she was pretty."
Gf: "...Does this skirt make me look fat?! She was skinnier than I am! Why'd she have to be so skinny? What is she, anorexic?!"
Bf: "You look fine. You're just feeling the jealousy and insecurity that can only be brought on by seeing your significant other's ex..."