What is the meaning of acute?

noun

• A mark (') placed above a vowel to indicate pronunciation.
  • synonyms: acute accent, ague

adjective

• Having or experiencing a rapid onset and short but severe course.
  • usage: "acute appendicitis"; "the acute phase of the illness"; "acute patients"
• Extremely sharp or intense.
  • usage: "acute pain"; "felt acute annoyance"; "intense itching and burning"
  • synonyms: intense
• Having or demonstrating ability to recognize or draw fine distinctions.
  • usage: "an acute observer of politics and politicians"; "incisive comments"; "icy knifelike reasoning"; "as sharp and incisive as the stroke of a fang"; "penetrating insight"; "frequent penetrative observations"
  • synonyms: discriminating, incisive, keen, knifelike, penetrating, penetrative, piercing, sharp
• Of an angle; less than 90 degrees.
• Ending in a sharp point.
  • synonyms: acuate, sharp, needlelike
• Of critical importance and consequence.
  • usage: "an acute (or critical) lack of research funds"