Defn: That point in which the three perpendiculars let fall from the angles of a triangle upon the opposite sides, or the sides produced, mutually intersect.
ORTHOCERAS
Or*thoc"e*ras, n. Etym: [NL., fr. Gr. (Paleon.)
Defn: An extinct genus of Paleozoic Cephalopoda, having a long, straight, conical shell. The interior is divided into numerous chambers by transverse septa.
ORTHOCERATITE
Or`tho*cer"a*tite, n. Etym: [Ortho- + Gr. (Zoöl.)
Defn: An orthoceras; also, any fossil shell allied to Orthoceras.
ORTHOCLASE
Or"tho*clase, n. Etym: [Ortho- + Gr. (Min.)
Defn: Common or potash feldspar crystallizing in the monoclinic system and having two cleavages at right angles to each other. See Feldspar.
ORTHOCLASTIC
Or`tho*clas"tic, a. (Crystallog.)
Defn: Breaking in directions at right angles to each other; — said of the monoclinic feldspars.
ORTHODIAGONAL
Or`tho*di*ag"o*nal, n. Etym: [Ortho- + diagonal.] (Crystallog.)