To lunge is to throw your body forward all at once, toward a person, an animal, or a thing, as if you mean to grab it, hit it, or catch it. A dog lunges at a stranger. In a fight, someone might lunge at you. The move is sudden: you close the space in one burst, not with a slow walk. You can use it as a noun too — a lunge, or a lunge for the bag. In fencing, a lunge is the long step you take when you stretch the sword arm toward the other person; that picture is close to the old meaning. Though actually, in a gym a lunge is a different scene. You step one leg forward, bend both knees, then push back. Nobody is attacking anybody. People still call it a lunge because the body shape looks like that fencing step. The word is ordinary English, a little dramatic. You meet it in stories, sport, and 'watch out' moments more than in calm office talk. It came from French allonge. Far back, the Latin pieces were ad, 'toward', and a verb from longus, 'long', so the first idea was stretching something out, making it longer. That still fits the fencing picture better than the 'jump to attack' picture, but English kept both.