What is the meaning of instant?

noun

• A very short time (as the time it takes the eye to blink or the heart to beat. )
  • usage: "if I had the chance I'd do it in a flash"
  • synonyms: blink of an eye, flash, heartbeat, jiffy, split second, trice, twinkling, wink, New York minute
• A particular point in time.
  • usage: "the moment he arrived the party began"
  • synonyms: moment, minute, second

adjective

• Occurring with no delay.
  • usage: "relief was instantaneous"; "instant gratification"
  • synonyms: instantaneous
• In or of the present month.
  • usage: "your letter of the 10th inst"
  • synonyms: inst
• Demanding attention.
  • usage: "clamant needs"; "a crying need"; "regarded literary questions as exigent and momentous- H. L. Mencken; "insistent hunger"; "an instant need"
  • synonyms: clamant, crying, exigent, insistent