D defs.my
Entry 4 senses Webster, 1913

Observer

/əb-zẽrv'-ẽr/ · Ob·serv·er · IPA /əbˈzɝvɚ/
01 n. One who observes, or pays attention to, anything; especially, one engaged in, or trained to habits of, close and exact observation; as, an …
  1. 1.
    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.
    “The observed of all observers.” Shak.
    “Careful observers may foretell the hour, By sure prognostic, when to dread a shower.” Swift.
  2. 2.
    One who keeps any law, custom, regulation, rite, etc.; one who conforms to anything in practice.
    “These . . . hearkened unto observers of times.” — Deut. xviii. 14.
  3. 3.
    One who fulfills or performs; as, an observer of his promises.
  4. 4.
    A sycophantic follower.[Obs.]