To draw something into the mouth by creating a vacuum with the lips and tongue. He sucked in the juice through a straw.
To cause someone to become involved in a situation or activity, often unwillingly. She got sucked in by the excitement of the crowd and joined the protest.
To take in or absorb something, such as air or a liquid. The vacuum cleaner sucked in all the dust from the carpet.
To pull or draw something inward, often by force. The whirlpool sucked in the small boat.