Chapter Oceanic to Octopodia of O by Webster's Dictionary (1913 Edition)

Regular octagon

, one in which the sides are all equal, and the angles also are all equal.

Octagonal
(Oc*tag"o*nal) a. Having eight sides and eight angles.

Octagynous
(Oc*tag"y*nous) a. [Octa- + Gr. wife.] (Bot.) Having eight pistils or styles; octogynous.

Octahedral
(Oc`ta*he"dral) a. [See Octahedron.] Having eight faces or sides; of, pertaining to, or formed in, octahedrons; as, octahedral cleavage.

Octahedral borax (Chem.), borax obtained from a saturated solution in octahedral crystals, which contain five molecules of water of crystallization; distinguished from common or prismatic borax. — Octahedral iron ore (Min.), magnetite.

Octahedrite
(Oc`ta*he"drite) n. (Min.) Titanium dioxide occurring in acute octahedral crystals.

Octahedron
(Oc`ta*he"dron) n. [Gr. fr. eight-side; (for eight) + seat, base, from to sit.] (Geom.) A solid bounded by eight faces. The regular octahedron is contained by eight equal equilateral triangles.

Octamerous
(Oc*tam"er*ous) a. [Octa- + Gr. part.] (Biol.) Having the parts in eights; as, an octamerous flower; octamerous mesenteries in polyps.

Octameter
(Oc*tam"e*ter) n. [Cf.L. octameter in eight feet. See Octa-, and meter.] (Pros.) A verse containing eight feet; as, —

Deep'b6 in|to'b6 the | dark'b6ness | peer'b6ing, | long'b6 I | stood'b6 there | wond''b6ring, | fear'b6ing.

Poe.

Octander
(Oc*tan"der) n. One of the Octandria.

Octandria
(||Oc*tan"dri*a) n. pl. [NL., fr. Gr. (for eight) + male, man.] (Bot.) A Linnæan class of plants, in which the flowers have eight stamens not united to one another or to the pistil.

Octandrian
(Oc*tan"dri*an Oc*tan"drous) a. (Bot.) Of or pertaining to the Octandria; having eight distinct stamens.

Octane
(Oc"tane) n. [See Octa-] . (Chem.) Any one of a group of metametric hydrocarcons (C₈H₁₈) of the methane series. The most important is a colorless, volatile, inflammable liquid, found in petroleum, and a constituent of benzene or ligroin.

Octangular
(Oc*tan"gu*lar) a. [L. octangulus eight-cornered; octo eight + angulus angle.] Having eight angles; eight-angled. — Oc*tan"gu*lar*ness, n.

Octant
(Oc"tant) n. [L. octans, - antis. fr. octo eight. See Octave.]

1. (Geom.) The eighth part of a circle; an arc of 45 degrees.

2. (Astron. & Astrol.) The position or aspect of a heavenly body, as the moon or a planet, when half way between conjunction, or opposition, and quadrature, or distant from another body 45 degrees.

3. An instrument for measuring angles having an arc which measures up to 9O°, but being itself the eighth part of a circle. Cf. Sextant.

4. (Math. & Crystallog.) One of the eight parts into which a space is divided by three coördinate planes.

Octapla
(||Oc"ta*pla) n.; etymol. pl., but syntactically sing. [NL., fr.Gr. (for eight) + -pla, as in E. hexapla; cf.Gr. eightfold.] A portion of the Old Testament prepared by Origen in the 3d century, containing the Hebrew text and seven Greek versions of it, arranged in eight parallel columns.