Definitions of acute:

• noun:   a mark (') placed above a vowel to indicate pronunciation
• adjective:   having or demonstrating ability to recognize or draw fine distinctions

  Example: "An acute observer of politics and politicians"

• adjective:   of an angle; less than 90 degrees
• adjective:   having or experiencing a rapid onset and short but severe course

  Example: "Acute appendicitis"

• adjective:   of critical importance and consequence

  Example: "An acute (or critical) lack of research funds"

• adjective:   extremely sharp or intense

  Example: "Acute pain"

• adjective:   ending in a sharp point