(n.) The approximate amount of time it takes for your mom to do something when she says "I'll be there in a minute"
General* conversion rate
1 mom minute= 15 normal minutes
*Please note that conversions vary. Moms may take up to 30 minutes or an hour after declaring their mom minute, and in those rare cases, they actually come in a minute.
Kid: "Hey Mom, can you come help me with my homework?"
Mom: "Yes, just a minute"
Kid: "Oh, ok, I guess that's a mom minute. I'll be back in 15 minutes, I'm gonna go watch some tv while I wait"
When a mother figure exaggerates the amount of minutes you did or didn't do something. She makes it from the amount of minutes it actually takes and says more, this in itself is it's own antonym. Due to this can be understating or exaggerating something.
Mom: You were supposed to be home 30 minutes ago!
Son: I was supposed to be home ten minutes ago. I don't know why your clock runs on mom minutes.