To sniff means to draw air into your nose with a quick, audible breath. You might sniff when you have a cold and your nose is running, or when you're trying to smell something like cookies baking in the oven. Dogs sniff constantly, using their powerful noses to gather information about their surroundings that we humans could never detect.

When you sniff something, you're actively trying to catch its scent. You might sniff a mysterious liquid to identify it, or sniff your milk to check if it's still fresh. Animals use sniffing to find food, recognize friends, and sense danger.

The word also describes the sound itself: that short, sharp intake of breath. If someone sniffs repeatedly during a sad movie, they might be trying not to cry. A quick sniff can express doubt or disapproval too: someone might give a dismissive sniff when they don't believe what they're hearing.

People sometimes say they can sniff out a problem, meaning they sense something wrong even without clear evidence, the way a bloodhound sniffs out a trail. When you catch a sniff of something, you've detected just a hint of it.