Noun

(en noun)

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

(biology) an organism that lives on or in another organism, 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.

* {{quote-magazine, date=2013-03

, author= , title=The Smallest Cell , volume=101, issue=2, page=83 , magazine= citation , passage=It is likely that the long evolutionary trajectory of Mycoplasma went from a reductive autotroph to oxidative heterotroph to a cell-wall–defective degenerate parasite . This evolutionary trajectory assumes the simplicity to complexity route of biogenesis, a point of view that is not universally accepted.}}

''Lice, fleas, ticks and mites are widely spread parasites .

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

* 1813 , (Percy Bysshe Shelley), Queen Mab , I:

Her golden tresses shade / The bosom’s stainless pride, / Curling like tendrils of the parasite / Around a marble column.

Noun

(countable, or, uncountable) Any one of various common types of small insects or animals which cause harm and annoyance.

The area was plagued by all sorts of vermin : fleas, lice, mice, and rats to name a few.

(countable, or, uncountable) Animals that prey on game, such as foxes or weasels.

(countable, or, uncountable) Obnoxious, or mean and offensive person or people.

Bring these gypsy vermin to the Palace of Justice.