Real Dictionary

make up
phrasal verb: If two people make up or make it up after a quarrel or disagreement, they become friends again.
phrasal verb: If you make up a bed, you put sheets and blankets on it so that someone can sleep there.
phrasal verb: If you make up an amount, you add something to it so that it is as large as it should be.
phrasal verb: If you make up something such as a story or excuse, you invent it, sometimes in order to deceive people.
phrasal verb: If you make up something such as food or medicine, you prepare it by mixing or putting different things together.
phrasal verb: If you make up time or hours, you work some extra hours because you have previously taken some time off work.
phrasal verb: If you make yourself up or if someone else makes you up, make-up such as powder or lipstick is put on your face.
phrasal verb: The people or things that make up something are the members or parts that form that thing.

make up in American English
to constitute; compose; form
to put together; compose; compound

make-up
Someone's make-up is their nature and the various qualities in their character.
uncountable noun: Make-up consists of things such as lipstick, eye shadow, and powder which some women put on their faces to make themselves look more attractive or which actors use to change or improve their appearance.
uncountable noun: The make-up of something consists of its different parts and the way these parts are arranged.

make-up in British English
noun: cosmetics, such as powder, lipstick, etc, applied to the face to improve its appearance
verb: to form or constitute