The following definitions are taken from Artlex On-Line Art Dictionary.
Collage (pr. kuhl-lahzh')
A picture or design created by adhering such basically flat elements as newspaper, wallpaper, printed text and illustrations, photographs, cloth, string, etc., to a flatsurface, when the result becomes three-dimensional, and might also be called a reliefsculpture / construction / assemblage. Most of the elements adhered in producing most collages are "found" materials. Introduced by the Cubist artists, this process was widely used by artists who followed, and is a familiar technique in contemporaryart.
"Collage" was originally a French word, derived from the word coller, meaning "to paste.”
Pablo Picasso, 1913-14, Head (Tête)
cut and pasted colored paper, gouache and charcoal on paperboard
43.5 x 33 cm,
Scottish National Gallery of Modern Art, Edinburgh
Robert Rauschenberg (American, 1925–2008
First Landing Jump
Medium: Cloth, metal, leather, electric fixture, cable, and oil paint on composition board, with automobile tire and wood plank
Dimensions: 7' 5 1/8" x 6' x 8 7/8" (226.3 x 182.8 x 22.5 cm)