What is the meaning of Overlay?

To lay, spread, or apply (something) over or across (something else); to overspread.

To overwhelm; to press excessively upon.

To lie over (someone, especially a child) in order to smother it; to suffocate.

To put an overlay on.

To bet too much money on.

An image to be overlaid on another; a superimposition or diapositive.

A piece of paper pasted upon the tympan sheet to improve the impression by making it stronger at a particular place.

Odds which are set higher than expected or warranted. Favorable odds.

A horse going off at higher odds than it appears to warrant, based on its past performances.

A decal attached to a computer keyboard to relabel the keys.

A block of program code that is loaded over something previously loaded, so as to replace the functionality.

A pop-up covering an existing part of the display.

A cravat.

A covering over something else.

simple past of overlie

Source: wiktionary.org