1 : a decoration on a surface made by pressing small pieces of colored glass or stone into a soft material that then hardens to make pictures or patterns
(count)
a church decorated with old mosaics
(noncount)
a picture done in mosaic
– often used before another noun
a mosaic floor
mosaic glass/tiles
2 : (count) : something made up of different things that together form a pattern — usually singular
a complex mosaic of islands
the country’s ethnic/political/religious/social mosaic