Real Dictionary

collage
You can refer to something that has been made by combining a number of very different things as a collage of a particular kind.
countable noun: A collage is a picture that has been made by sticking pieces of coloured paper and cloth onto paper.
uncountable noun: Collage is the method of making pictures by sticking pieces of coloured paper and cloth onto paper.

collage in American English
an art form in which, variously, small objects, bits of newspaper, cloth, pressed flowers, etc. are pasted together on a surface in incongruous relationship for their symbolic or suggestive effect
to arrange (material) in a collage
noun: a technique of composing a work of art by pasting on a single surface various materials not normally associated with one another, as newspaper clippings, parts of photographs, theater tickets, and fragments of an envelope
transitive verb: to make a collage of

collage in British English
noun: an art form in which compositions are made out of pieces of paper, cloth, photographs, and other miscellaneous objects, juxtaposed and pasted on a dry ground