1something laid as a covering over something else:a durable, cost-effective floor overlay
a transparent sheet placed over artwork or something such as a map, giving additional information or detail:full-colour aerial photographs with overlays showing suggested routes
2 [mass noun] Computing the process of transferring a block of program code or other data into internal memory, replacing what is already stored.
[count noun] a block of code or other data transferred during the overlay process.
overlay in other Oxford dictionaries
Definition of overlay in the US English dictionary
