noun

• (US, archaic) Synonym of bangs: hair hanging over the forehead, especially a hairstyle with such hair cut straight across.
  "Tiffany has long hair and bangs."
• (chiefly US) The symbol !, known as an exclamation point.
  "An e-mail address with an ! is called a bang path."
• (mathematics) A factorial, in mathematics, because the factorial of n is often written as n!
• (vulgar, slang) An act of sexual intercourse.

verb

• (intransitive) To make sudden loud noises, and often repeatedly, especially by exploding or hitting something.
  "The fireworks banged away all through the night."
• (ambitransitive) To hit hard.
  "He banged the door shut."
• (slang, ambitransitive, vulgar) To engage in sexual intercourse.
  "We can hear the couple banging upstairs."
• (with "in") To hammer or to hit anything hard.
  "Hold the picture while I bang in this nail."