A year and a half ago I made a post on the Anti D&D Movement relating my experience being a D&D geek back in the early 80s. A got a comment by Jennifer yesterday related her experience trying to explain D&D to her mother. It brought to mind my own attempts.
When all else fails I say it a form of improvisational theater performed among friends. That seems to leave the listener with a "oh I get it" expression.
Getting Out of My Own Way
1 hour ago