either a design that is fixed to some surface or a paper bearing the design which is to be transferred to the surface
"The children carefully peeled the sports car decal from its backing sheet and pressed it onto their bedroom wall."
A design or picture produced in order to be transferred to another surface either permanently or temporarily.
"The children spent hours applying colorful decals to their bedroom furniture and toy cars."
In plain English: A decal is a sticker with an image that you stick onto something smooth, like a car window or water bottle.
"The children used bright animal decals to decorate their bedroom walls."
Usage: Decals are often confused with stickers, but they differ because decals use a water-activated adhesive that requires soaking before application, whereas most stickers stick directly to the surface. Use "decal" specifically for designs intended for transfer onto glass, metal, or plastic rather than paper-based temporary labels.
To apply decals to.
"The artist carefully decal the intricate floral pattern onto the ceramic mug before firing it in the kiln."
The word decal is a shortened form of decalsomania. It entered English as an informal abbreviation to refer specifically to the decorative transfer sheets used for applying designs to surfaces.