A compound word is one word created by adding two words together. In Spanish, compound nouns are often created by attaching the plural form of a noun to the base of a verb. These words always look plural and sometimes even look feminine, but a compound noun is always masculine and is the same in its singular and plural form.
For example:
abre (opens) + latas (cans) = el abrelatas (the can opener) or los abrelatas (the can openers)
quita (to take away, remove) + manchas (stains) = el quitamanchas (stain remover) or los quitamanchas
rasca (scrapes) + cielos (skies) = el rascacielos (the skyscraper) or los rascacielos (the skyscrapers)