(noun) - Décollage comes from the French word décoller (take off, unstick). In art, we refer to décollage as a technique based on the appearance of advertisements ripped from billboards. The result leaves fragments of papers and the layering of previous posters.
The Italian modernist artist Mimmo Rotella (1918-2006), was best known for his Décollage pieces, a sort of NeoDada, anti-Cubist collage guesture. He was part of the Nouveau Realistes movement.
Décollage in French also means "take off" during airplane travel.
Sometimes the word "décollage" is mistakenly used in place of décolletage. Décolletage refers to a low-cut neckline. (Décolleté is another way to say décolletage.) So if your friend refers to a woman's cleavage as "décollage," feel free to point out the absence of ripped posters on her chest.