Definition of observer

• n. - One who observes, or pays attention to, anything; especially, one engaged in, or trained to habits of, close and exact observation; as, an astronomical observer.
• n. - One who keeps any law, custom, regulation, rite, etc.; one who conforms to anything in practice.
• n. - One who fulfills or performs; as, an observer of his promises.
• n. - A sycophantic follower.