Unsuspecting means not aware that something is about to happen, especially something surprising or dangerous. An unsuspecting person has no idea what's coming.

When your friends plan a surprise birthday party, you're the unsuspecting guest of honor, going about your day with no clue that everyone's hiding in your living room. When a magician performs a trick, the unsuspecting audience members don't know how the illusion works or what will happen next.

The word often appears in stories where someone is about to be tricked, startled, or caught off guard. A cartoon cat might sneak up on an unsuspecting mouse. A prankster might hide behind a door, waiting to jump out at an unsuspecting person. In mysteries, criminals target unsuspecting people who seem like easy marks because they're not paying attention or don't sense any danger.

Being unsuspecting isn't the same as being careless or foolish. It simply means you have no reason to expect what's about to occur. The substitute teacher walking into your classroom on April Fools' Day is unsuspecting, while you and your classmates know exactly what pranks await. Sometimes being unsuspecting just means you trust that everything is normal, which makes surprises, both good and bad, work so well.