Definitions of make up:

• verb:   make up work that was missed due to absence at a later point

  Example: "I have to make up a French exam"

• verb:   apply make-up or cosmetics to one's face to appear prettier
• verb:   devise or compose
• verb:   put in order or neaten

  Example: "Make up a room"

• verb:   do or give something to somebody in return
• verb:   form or compose
• verb:   come to terms
• verb:   make up something artificial or untrue