Wacky means amusingly odd or silly in an over-the-top, zany way. A wacky science experiment might involve launching marshmallows across the classroom to study projectile motion. A wacky outfit could mean wearing mismatched socks, a superhero cape, and swimming goggles to school on crazy hat day.

The word suggests something that's strange but fun, weird but harmless. Wacky describes things that are noticeably, cheerfully bizarre. A kid who tells wacky jokes might make up absurd stories about penguins who drive school buses or teachers who secretly live on the moon. A wacky inventor creates contraptions that look ridiculous but somehow work, like a hat with an umbrella attachment or a robot that serves breakfast in bed.

You might describe a comedy show as wacky if the characters do unpredictable, goofy things that make you laugh. The word captures that feeling when something is so silly and unexpected that you can't help but smile. Wacky things don't take themselves too seriously, and that's exactly what makes them entertaining.