What is the meaning of improvised?

verb

• Perform without preparation.
  • usage: "he extemporized a speech at the wedding"
  • synonyms: improvise, improvize, ad-lib, extemporize, extemporise
• Manage in a makeshift way; do with whatever is at hand.
  • usage: "after the hurricane destroyed our house, we had to improvise for weeks"
  • synonyms: improvise, extemporize

adjective

• Done or made using whatever is available.
  • usage: "crossed the river on improvised bridges"; "the survivors used jury-rigged fishing gear"; "the rock served as a makeshift hammer"
  • synonyms: jury-rigged, makeshift