Underhand means done in a sneaky, dishonest, or secretive way to gain an advantage or hide your true intentions. When someone uses underhand tactics, they're working behind the scenes in ways they wouldn't want others to know about.

Imagine a student who pretends to be your friend but secretly tells the teacher things to get you in trouble, or someone who spreads rumors while acting innocent. These are underhand behaviors because they're hidden and manipulative. In sports, an underhand deal might involve secretly paying players to lose on purpose. In business, underhand methods might include lying about a competitor to steal their customers.

The word suggests something worse than simple dishonesty: it implies calculation and sneakiness. Someone acting in an underhand way knows what they're doing is wrong and deliberately hides it. You might hear someone say “That was pretty underhand” when they discover a friend has been working against them in secret.

The word can also describe a throwing motion where your hand stays below your shoulder, moving upward from below, like tossing a softball underhand. But when describing behavior rather than throwing, underhand always carries that sense of sneakiness and dishonesty.