Swine is another word for pigs or hogs. A farmer might raise swine for meat, and a veterinarian who specializes in treating farm animals needs to understand swine health and behavior. The word can refer to a single pig or many pigs: you might say “That swine got loose from the pen” or “The farm raises swine.”

The word is also used as an insult for someone acting selfishly, greedily, or rudely. If someone pushes to the front of a lunch line and grabs all the best food, another student might mutter, “What a swine!” This usage isn't fair to actual pigs, which are intelligent, social animals, but the insult has stuck around for centuries.

Swine sounds more formal or old-fashioned than just saying “pig.” You're more likely to encounter it in farming contexts, older books, or when someone wants to sound especially indignant about bad behavior. The fairy tale about the three little pigs could just as easily be called “The Three Little Swine,” though that would sound rather stuffy.