State of being lively, energetic, loud, outgoing, unreserved, and sometimes even obnoxious in public (usually at a party) without any prior consumption of alcohol. It's as if one has become drunk on life or from the energy of the party atmosphere. One may be subject to moodswings, especially as the party dies down, experiencing a sort of social buzzkill, leading to minor temporary depression and fatigue. Occasionally, one's memory may even be impaired, as one may be reminded later about things that were said or done that one does not remember doing or saying.
It's fun, safe, and you can drive yourself home afterward!
At Heather's Halloween Party, I was socially drunk because she came outside and told me to shut up because I was the loudest (and only sober) one there, and that I was going to get the police called on the party. But I wasn't going to get in trouble because I wasn't even drinking!