To adorn unnecessarily something already beautiful. The expression is a condensation of Shakespeare's metaphor in King John: "To gild refined gold, to paint the lily ... is wasteful and ridiculous excess." i.e., you wouldn't need to add gold to a beautiful lily.
by _Andy_ June 24, 2006
by Fredrickthestick March 13, 2014
To gild something is to cover it with gold. A nice vagina looks like a flower. So when a woman wants to go take a piss she'll call it "Gild the Lilly" when in mixed company.
by St. Peter Dickinson February 26, 2017