Defn: The act of darkening; the state of being darkened; darkness.
[Obs.]
In every megrim or vertigo, there is an obtenebration joined with a
semblance of turning round. Bacon.

OBTENSION
Ob*ten"sion, n. Etym: [L. obtentio. See Obtend.]

Defn: The act of obtending. [Obs.] Johnson.

OBTEST
Ob*test", v. t. [imp. & p. p. Obtested; p. pr. & vb. n. Obtesting.]
Etym: [L. obtestari; ob (see Ob-) + testari to witness, fr. testis a
witness.]

1. To call to witness; to invoke as a witness. [R.] Dryden.

2. To beseech; to supplicate; to beg for. [R.]

OBTEST
Ob*test", v. i.

Defn: To protest. [R.] E. Waterhouse.

OBTESTATION
Ob`tes*ta"tion, n. Etym: [L. obtestatio.]

Defn: The act of obtesting; supplication; protestation. [R.]
Antonio asserted this with great obtestation. Evelyn.