verb

• (transitive) To quickly lower (the head or body), often in order to prevent it from being struck by something.
  "As some raw youth in country bred, To arms by thirst of honour led, When at a skirmish first he hears The bullets whistling round his ears, Will duck his head aside"
• (transitive) To lower (something) into water; to thrust or plunge under liquid and suddenly withdraw.
  "Adams after ducking the Squire tvvice or thrice leaped out of the Tub, […]"
• (intransitive) To go under the surface of water and immediately reappear; to plunge one's head into water or other liquid.
  "[…]In Tiber ducking thrice, by break of day[…]"
• (intransitive) To bow.
  "The Learned pate / Duckes to the Golden Foole."

noun

• (caving) A cave passage containing water with low, or no, airspace.

noun

• (uncountable) The flesh of a duck used as food.
• (cricket) A batsman's score of zero after getting out. (Short for duck's egg.)
• (slang) A playing card with the rank of two.
• (US) A cairn used to mark a trail.

noun

• (in the plural) Trousers made of such material.
  "And they would go up and find old Allington, in white ducks, standing in the fringe of long grasses and cow-parsley on the other edge of the island, looking to his poultry or his rabbits."