intransitive verb
Definition: To lower the head or body quickly, often to avoid something or to hide.
Example: He had to duck to avoid hitting his head on the door frame.
noun
Definition: A waterbird with a broad body, short legs, and a flat bill, often found in ponds and lakes.
Example: We saw a duck swimming in the pond.
transitive verb
Definition: To lower the body quickly to avoid something or to push something under water.
Example: He ducked to avoid the flying ball.