What is the meaning of ad-lib?

noun

• Remark made spontaneously without prior preparation.
  • usage: "his ad-libs got him in trouble with the politicians"

verb

• Perform without preparation.
  • usage: "he extemporized a speech at the wedding"
  • synonyms: improvise, improvize, extemporize, extemporise

adjective

• With little or no preparation or forethought.
  • usage: "his ad-lib comments showed poor judgment"; "an extemporaneous piano recital"; "an extemporary lecture"; "an extempore skit"; "an impromptu speech"; "offhand excuses"; "trying to sound offhanded and reassuring"; "an off-the-cuff toast"; "a few unrehearsed comments"
  • synonyms: extemporaneous, extemporary, extempore, impromptu, offhand, offhanded, off-the-cuff, unrehearsed
• Said or done without having been planned or written in advance.
  • usage: "he made a few ad-lib remarks"
  • synonyms: spontaneous, unwritten