Furtive means sneaky or secretive in a way that suggests you're doing something you shouldn't be doing. When someone makes a furtive glance, they're looking quickly and carefully, hoping nobody notices. A student might take a furtive peek at their phone during class, or someone might make a furtive grab for the last cookie when they think no one's watching.

The word carries a feeling of guilt or nervousness. Furtive behavior looks suspicious because the person is clearly trying not to get caught, moving with deliberate stealth and showing signs of worry. A detective might notice a suspect's furtive movements, or a teacher might spot a furtive exchange of notes between students.

You can act furtively even when you're not doing anything wrong. If you're planning a surprise party, you might furtively hide decorations or speak in hushed tones when the birthday person walks by. But furtive usually describes the nervous, guilty behavior of someone who knows they're breaking a rule or doing something questionable. The shifty eyes, the quick movements, the constant checking to see if anyone's watching: that's furtive behavior, and it usually gives people away faster than they realize.