1. an organism that lives in or on another organism and gets food or other benefits from it while usually harming the host
Usage: biology
2. a person who lives off others without giving anything useful in return
Usage: disapproving

Examples

• Fleas are parasites that live on dogs and cats.
• The tapeworm is a parasite found in the human intestine.
• Many tropical diseases are caused by parasites.
• He’s just a parasite who never pays his share of the rent.
• She called him a parasite for always borrowing money but never paying it back.
• The scientist studied how parasites affect their host organisms.
• Some parasites can actually benefit their hosts in certain situations.