to coat with gold, gold leaf, or a gold-colored substance.
to give a bright, pleasing, or specious aspect to.
Archaic. to make red, as with blood.
gild the lily, to add unnecessary ornamentation, a special feature, etc., in an attempt to improve something that is already complete, satisfactory, or ideal: After that wonderful meal, serving a fancy dessert would be gilding the lily.
Origin of gild
1300–50;Middle Englishgilden,Old English-gyldan; akin to gold
Old English gyldan "to gild, to cover with a thin layer of gold," from Proto-Germanic *gulthianan (cf. Old Norse gylla "to gild," Old High German ubergulden "to cover with gold"), from *gulthan "gold" (see gold). Related: Gilded; gilding. Figuratively from 1590s.
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]