What is the meaning of prolong?

verb

• Lengthen in time; cause to be or last longer.
  • usage: "We prolonged our stay"; "She extended her visit by another day"; "The meeting was drawn out until midnight"
  • synonyms: protract, extend, draw out
• Lengthen or extend in duration or space.
  • usage: "We sustained the diplomatic negotiations as long as possible"; "prolong the treatment of the patient"; "keep up the good work"
  • synonyms: sustain, keep up