Sidelong means directed to the side rather than straight ahead. When you glance sidelong at someone, you look at them from the corner of your eye without turning your head fully toward them. A sidelong look can happen when you're trying to be subtle, like checking to see if your teacher noticed you whispering to a friend, or when you're curious about something but don't want to stare directly.

The word can describe any sideways movement or position. A crab scuttles sidelong across the beach. You might take a sidelong step to squeeze past someone in a crowded hallway.

Sidelong glances often carry meaning beyond just the direction of the look. A sidelong glance can express suspicion, curiosity, doubt, or even admiration. In stories, characters exchange sidelong looks when they want to communicate without words, perhaps sharing a secret joke or silently questioning whether to trust someone. That indirect, sideways quality is what makes the word particularly useful for describing moments when people are being watchful, cautious, or communicating something they don't want to say out loud.