OCTAVO
Oc*ta"vo, a.

Defn: Having eight leaves to a sheet; as, an octavo form, book, leaf, size, etc.

OCTENE
Oc"tene, n. Etym: [See Octo-.] (Chem.)

Defn: Same as Octylene.

OCTENNIAL Oc*ten"ni*al, a. Etym: [L. octennium a period of eight years; octo eight + annus year.]

Defn: Happening every eighth year; also, lasting a period of eight
years. Johnson.
— Oc*ten"ni*al*ly, adv.

OCTET
Oc*tet", n. Etym: [From L. octo eight, like E. duet, fr.L.duo. See
Octave.] (Mus.)

Defn: A composition for eight parts, usually for eight solo instruments or voices.

OCTIC
Oc"tic, a. Etym: [Octo- + -ic.] (Math.)

Defn: Of the eighth degree or order.
— n. (Alg.)