The point in a relationship when you are officially dating someone even if you haven't had the 'are we dating' conversation. Several drunken sleepovers may have occured at this point but once a Tuesday rolls around, you watch a movie together, and have a alcohol free sleepover...you are dating.
Ben: How are things with Julie? You've been hanging out a ton. Are you all dating yet?
Rich: Good, but no way we've only hung out 3 or 4 times.
Ben: Have you had a sober sleepover?
Ben: Dude, you're totally dating.