A Imum's worst trait is thinking they are "entitled to something" often asking for several favors in a single day.
Don't expect anything in return from an Imum, they are very self centered and only care about themselves.
A Imum can also be used to describe someone with very poor personal hygiene skills.
A Imum will cause an argument at every opportunity and put other people down in a pathetic attempt to make himself/herself feel better.
That person has such nasty splotchy white teeth, totally an Imum!