Add unnecessary adornment or supposed improvement. For example, Offering three different desserts after that elaborate meal would be gilding the lily. This expression is a condensation of Shakespeare's metaphor in King John (4:2): “To gild refined gold, to paint the lily ... is wasteful and ridiculous excess.” [c. 1800]

To adorn unnecessarily something that is already beautiful or perfect: “Morty had us all believing his tall tale until he couldn't resist gilding the lily.”