Dryly means speaking or writing in a subtle, understated way that makes something funny or ironic without obvious emotion or excitement. When someone responds dryly, they might say something clever or sarcastic, but their face stays straight and their voice stays flat, which can make the comment even funnier.

Imagine a teacher who, after a student gives a ridiculous excuse for missing homework, says in a completely calm, matter-of-fact voice: “How fascinating. I've never heard that particular dog-ate-my-homework story before.” That's speaking dryly. The humor comes from the contrast between what's being said and how it's being said.

Dry humor or dry wit relies on cleverness rather than exaggeration or silliness. Mark Twain often wrote dryly, making sharp observations about human nature in a calm, straightforward style that made his points even more powerful. When someone remarks dryly, “Well, that went exactly as planned,” after something goes completely wrong, everyone knows they're being ironic, but the flat delivery makes it memorable.