Hilariously means in a way that is extremely funny or causes a lot of laughter. When something happens hilariously, it's so funny that people can't help but laugh out loud.

You might describe a comedy show as hilariously funny if it had you and your friends doubled over with laughter. A classmate's attempt to juggle tennis balls might end hilariously when they all bounce off their head at once. Sometimes things are funny in unexpected ways: a serious documentary about penguins might include hilariously awkward footage of them slipping on ice.

When you say something was hilariously bad, you mean it was so terrible that it actually became funny, like when a movie's special effects are so obviously fake that everyone starts giggling.

Hilariously suggests the kind of deep, genuine laughter that makes your stomach hurt: the real thing that leaves you breathless. If your dad tells a joke that's only slightly funny, you might smile. But if he slips on a banana peel in a perfectly cartoonish way, that's hilariously funny.