1. Seeing/feeling a pair of boobs that make you celebrate due to their largeness/shape/whatever you like really.
2. Seeing another girl in the showers and realising your boobs are better than hers in some way
1. When I motorboated that girl with the E cups, I was so resisting the urge to do a boobilation there and then, they were that epic.
2. Her boobs were actually smaller than mine so in my head I did a boobilation.