Engagement in sexual relations with one's best friend or "bestie." A relationship that is higher than Fuck Buddies, but lower than actually dating. Will either end in blissful marriage or utter destruction of the friendship.
~"Hey, are Mark and Kathy dating? I thought they were just friends."
~"They're not dating, they're just into bestie-ality"
~"They're not dating, they're just into bestie-ality"
by RussBus February 12, 2010