parasite

(derogatory) A person who lives on other people's efforts or expense and gives little or nothing back.

(derogatory) A sycophant or hanger-on.

(biology) An organism that lives on or in another organism of a different species, deriving benefit from living on or in that other organism, while not contributing towards that other organism sufficiently to cover the cost to that other organism.

(literary, poetic) A climbing plant which is supported by a wall, trellis etc.

(historical) A retainer or companion of an ancient Celtic warrior, who praised him in song or poetry at gatherings; a bard.

(aviation) A component of a composite aircraft which is carried aloft and air-launched by a larger carrier aircraft or mother ship to support the primary mission of the carrier.