a suckubis is a health sucking demon causing people to become mentaly ill.
"i used to be okay untill my wife be came a suckubis and left me."
a woman/man, with whom you engage in a romantic relationship, that alienates you from all your friends and/or family.
This person also has such an effect on you that they manage to spend all your time with you. You think they are the greatest person in the world, hence, enabling you to not care that they are slowly sucking the life out of you and your platonic relationships with friends and family.
friend 1: whatever happened to brandon?
friend 2: he hooked up with suzanna. she is a suckubis...
friend 3: id like to slap her in the face!