A piranha is a small freshwater fish from South America known for its razor-sharp teeth and powerful jaws. Piranhas live in rivers like the Amazon, swimming in large groups called schools. They have triangular teeth that interlock like a zipper, letting them bite through meat, seeds, and fruits with surprising force.

Despite their fearsome reputation in movies, piranhas rarely attack humans. They mostly eat other fish, insects, and plants. The dangerous stories come from a few species that can become aggressive when trapped in shrinking pools during dry seasons, competing desperately for food. Most of the time, piranhas are actually quite skittish and swim away from larger animals.

Scientists have identified about 60 species of piranha, and only a handful are known for aggressive feeding behavior. Some piranhas are even vegetarian, munching on fruits that fall into the river.

People sometimes use piranha as a metaphor for aggressive competitors. In business, someone might describe fierce rivals as piranhas circling their prey. The image suggests quick, ruthless behavior, though real piranhas are far more cautious than their Hollywood portrayals suggest.