n.
a solitary experience you wish you could have shared with someone else—having dinner in a romantic setting, reaching the summit after an arduous climb, having a run-in with a crazy stranger that nobody’s going to believe—which makes you look around for confirmation that it even happened at all.
Welsh si-so, see-saw, an invention that can only ever be enjoyed by multiple people; when used alone, it’s just a wonky bench. Pronounced “see-soh.”