An Under Armour Mom is a woman between the age of 25 and 50 (there have been sightings of UAM's up to 65 years old, however) who has children, is currently married or divorced, and thinks she is an athlete. She attends yoga class every now and then, she might even go for a quick jog with her baby in the stroller, or participate in a triathlon "for the challenge" (rides a mountain bike with aero bars, doesn't really know how to swim). Due to her active and healthy lifestyle which makes her better than everyone else, she requires that her clothing express her passion for moderate exercise to her peers. She will regularly spend hundreds of dollars on Under Armour clothing and wears it on a regular basis even when not "training". T-Shirts that say "ATHLETE" on them, or "TRAIN HARD" or "PROTECT THIS HOUSE" are slogans of choice. When it's cold outside, she needs some "Coldgear". When it's hot outside, she seems some "Heatgear". The performance enhancing microfibers help her perform better, whether it be kicking the soccer ball around with her family, or picking up a pizza in her gigantic SUV.
She is a poser.
Some guy: Wow look at all that Under Armour gear that lady just bought, she must be preparing for some serious athletic training in the near future.
Another guy: Yeah, she's so cool. I wish I was an athlete just like her.
Under Armour Mom: *puts on earbuds playing Journey's greatest hits and power walks in the mall*