A whopper is something remarkably large or extreme. When someone catches a whopper of a fish, it's impressively, almost unbelievably huge. The word carries a sense of exaggeration or amazement: a whopper of a storm might dump three feet of snow overnight, and a whopper of a mistake might be accidentally deleting your entire book report the night before it's due.

The word also means a big lie, especially one that's so outrageous you might wonder how anyone expected to get away with it. If your friend claims they scored 500 points in a basketball game, that's a whopper. The word suggests the lie is boldly, almost comically untrue.

Both meanings share the idea of something oversized. Whether it's an enormous thing or an enormous fib, a whopper stands out because of its remarkable size. When someone says “that's a whopper,” they might be impressed by something's actual bigness, or they might be calling out an unbelievable claim.