Overlay的意思是覆盖物，覆盖层。中英文例句如下：

The map had an overlay of topographic details. （这张地图上覆盖着一层地形细节。）

The city was covered by a blanket of smog, an environmental overlay that significantly reduced visibility. （这座城市被一层烟雾笼罩，这种环境覆盖物严重降低了能见度。）

The researchers used a computer program to overlay the satellite images onto a digital map of the region. （研究人员使用计算机程序将卫星图像叠加在该地区的数字地图上。）