1. Something that is done by a large amount, or in a way that is easily noticeable: "Those who smoke cigarettes have a significantly greater risk of developing lung cancer than people who don't smoke."
2. Done in a way which is large or important enough to be noticed or to have an effect: "The store down the street sold the book for a significantly lower price than this one here."
3. That which is done in a way that has a special or hidden meaning: "Her mother glanced significantly in her son's direction when she said that someone had not done his homework."