A low two is when a man's balls smack a female's bottom during a celebratory final thrust after great sex. Like a high five.
L: We had to low two after sex last night; it was that good. Balls deep with a satisfying smack!
Rather than a high five, the low two is when you butt bump someone.
In Modern Family, Cameron says to Jay "oh sure when you're gay you just walk around giving butt bumps to everybody... it's like a high five, it's a low two"
Similar to a High-Five, the Low Two is when two dudes' balls slap together in the act of double penetrating a woman.
Yo, Jeff, gimme a low two, cause this hood-rat can take it to the base!