Top definition
This is a phrase a mother uses to assert herself over her children. In one simple sentence she shows dominance over her offspring and reminds her children that she does does not have to explain herself or her decisions to them.

This is a phrase used by a mom when her child...
A.) Has done something wrong and mom is telling him or her to stop.
B.) Is about to do something wrong and is caught and mom tells him or her not do it.
C.) Is asking for something and Mom says, "No!".

In all of these instances the child would more than likely repeat this phrase, "But why"! In the beginning the mother may say, "Im the Mommy that's why", but usually the mother will say no several times until she feels like she going to explode.
(In the grocery store)

Little Joey: Mommy can we get donuts from the bakery.
Mom: Not today sweety
Joey: Please Mom
Mom: No, Joey, not today.
Joey: (Starts to fake cry) Its not fair, you never get me anything.
Mom: Thats not true, stop with the fake tears and a big a boy or youre going to be in trouble.
Joey: (He raises his voice) Just tell me why, mommy. Why cant we get them? Why?

Mom: (Mom lowers her voice into a growl and gets close to Joey face) I'm the Mommy that's why!
by PsychStudent101 July 21, 2016
Get the mug
Get a I'm the Mommy that's why! mug for your cat Riley.