A surfeit is an excessive amount of something, usually more than you want or need. If you eat a surfeit of Halloween candy, you've had way too much and probably feel sick. When there's a surfeit of rain, your backyard turns into a swampy mess.

The word carries a sense of overload and discomfort. A little bit of something might be pleasant, but a surfeit crosses into “too much of a good thing.” A few video games before dinner is fine, but a surfeit of screen time leaves you tired and restless. One slice of birthday cake tastes delicious, but a surfeit of cake makes your stomach hurt.

You'll often see surfeit used for things that seem positive in moderation but become problems in excess. A library might have a surfeit of mystery novels but too few science books. A student might complete their homework efficiently but struggle with a surfeit of after-school activities that leave no time for rest or play.

As a verb, to surfeit someone means to give them so much of something that they feel uncomfortable or sick of it.