Defn: The office or work of an observer.
OBSERVING
Ob*serv"ing, a.
Defn: Giving particular attention; habitually attentive to what passes; as, an observing person; an observing mind. — Ob*serv"ing*ly, adv.
OBSESS Ob*sess", v. t. Etym: [L. obsessus, p.p. of obsidere to besiege; ob (see Ob-) + sedere to sit.]
Defn: To besiege; to beset. Sir T. Elyot.
OBSESSION
Ob*ses"sion, n. Etym: [L. obsessio: cf.F. obsession.]
1. The act of besieging. Johnson.
2. The state of being besieged; — used specifically of a person beset by a spirit from without. Tylor. Whether by obsession or possession, I will not determine. Burton.
OBSIDIAN Ob*sid"i*an, n. Etym: [L. Obsidianus lapis, so named, according to Pliny, after one Obsidius, who discovered it in Ethiopia: cf.F. obsidiane, obsidienne. The later editions of Pliny read Obsianus lapis, and Obsius, instead of Obsidianus lapis, and Obsidius.] (Min.)
Defn: A kind of glass produced by volcanoes. It is usually of a black color, and opaque, except in thin splinters.