Impeccability, when speaking of God, means the inability to sin. Christ was impeccable in that He could not sin and He did not sin (1 Peter 2:22). There is a dispute as to whether or not Jesus could have sinned since He was a man as well as divine. But Jesus, the person, claimed the attributes of both divinity and humanity (see Communicatio Idiomatum). That is, He knew all things, could forgive sins, etc., but also was hungry and had to sleep. Since the divine attributes as well as the human attributes were ascribed to Jesus and the divine attribute means that God cannot sin, it is logical to conclude that Jesus could not have sinned.