6. Laugh, chuckle, grin, smile refer to methods of expressing mirth, appreciation of humor, etc. A laugh may be a sudden, voiceless exhalation, but is usually an audible sound, either soft or loud: a hearty laugh. Chuckle suggests a barely audible series of sounds expressing private amusement or satisfaction: a delighted chuckle. A smile is a (usually pleasant) lighting up of the face and an upward curving of the corners of the lips (which may or may not be open); it may express amusement or mere recognition, friendliness, etc.: a courteous smile. A grin, in which the teeth are usually visible, is like an exaggerated smile, less controlled in expressing the feelings: a friendly grin.

Did you mean light up?