Parasite

One who frequents the tables of the rich, or who lives at another's expense, and earns his welcome by flattery; a hanger-on; a toady; a sycophant.

A plant obtaining nourishment immediately from other plants to which it attaches itself, and whose juices it absorbs; -- sometimes, but erroneously, called epiphyte.

A plant living on or within an animal, and supported at its expense, as many species of fungi of the genus Torrubia.

An animal which lives during the whole or part of its existence on or in the body of some other animal, feeding upon its food, blood, or tissues, as lice, tapeworms, etc.

An animal which steals the food of another, as the parasitic jager.

An animal which habitually uses the nest of another, as the cowbird and the European cuckoo.

an animal or plant that lives in or on a host (another animal or plant); it obtains nourishment from the host without benefiting or killing the host

a follower who hangs around a host (without benefit to the host) in hope of gain or advantage