Noah Webster
Observant
OBSERV'ANT, adjective s as z.
1. Taking notice; attentively viewing or noticing; as an observant spectator or traveler.
2. Obedient; adhering to in practice; with of. He is very observant of the rules of his order.
We are told how observant Alexander was of his master Aristotle.
3. Carefully attentive; submissive.
OBSERV'ANT, noun s as z.
1. A slavish attendant. [Not in use.]
2. A diligent observer.