step-moster 

1. A woman who marries someone who has children who are in her same age group, yet insists on condesending labels such as "son" or "daughter" when introducing her new relatives.
2. sounds like step-monster.
3. a cross between mother and sister
4. someone who is the same age or younger than you who controls your dad, especially, if they do and say tacky things when he is not around.

My step-moster was running around the house in her underware again...

step-moster by cindedarkey January 22, 2008

stepmonster 

The word used to identify a stepmother that you don't like, get along with, just plain despise. 1st coined in the film St. Elmo's Fire, used chiefly by Demi Moore's character, Jules.

Jules: I have to go. Did the hospital call? Did my stepmonster die?

stepmonster by Tommyt August 25, 2008

stepmonster 

A step mother who is a nightmare to the other children. Known to fight for the mother title in many sinister ways. Pouts when the real mother is in contact with the child or grandchildren. Has no concern about how that looks to anyone..kids, grandkids. A total "one-upper" in every breath

Dammit, my stepmonster Lisa wont leave my mother alone. I mean who do she thinks she is, she has never been and will never be a mother to me

stepmonster by llp1964 April 3, 2009

Serbian Stepmaster 

When a floor installer usually of Serbian or possibly Romanian background is installing flooring on a staircase, but is so drunk they are unable to balance on one step and continuously fumble between two or more steps in an effort to maintain balance. This is usually done with a beer or brandy in hand and possibly a cel phone in the other hand. This exercise type of work could be the reason said person will likely be wearing track pants and a wife beater

Goran : What the hell is Dragan doing? He's so drunk he can't even balance on one step
Andrej: That bastard has been doing the Serbian stepmaster since noon!

Serbian Stepmaster by BaldFatGuy May 18, 2011