OVERLAY

v. & n. --v.tr. (past and past part. -laid) 1 lay over. 2 (foll. by with) cover the surface of (a thing) with (a coating etc.). 3 overlie. --n. 1 a thing laid over another. 2 (in printing, mapreading, etc.) a transparent sheet to be superimposed on another sheet. 3 Computing a the process of transferring a block of data etc. to replace what is already stored. b a section so transferred. 4 a coverlet, small tablecloth, etc.