Tit juggling
When a large-breasted lady runs, jumps or does anything that makes her breasts move independently of one another (one going up as the other descends, for instance) she is performing the act of tit juggling.
"Hey, did you see Brenda running to catch the bus today? Major tit juggling!"
Juggling Tits
When you are around as many topless girls that you are metaphorically Juggling Tits
Will: How many girls were you with last night?
Noah: Man, there were so many girls I was Juggling Tits
Noah: Man, there were so many girls I was Juggling Tits