octave

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The interval of eight diatonic degrees between two tones of the same name, the higher of which has twice as many vibrations per second as the lower.
• noun A tone that is eight diatonic degrees above or below another given tone.
• noun Two tones eight diatonic degrees apart that are sounded together.
• noun The consonance that results when two tones eight diatonic degrees apart are sounded.
• noun A series of tones included within this interval or the keys of an instrument that produce such a series.
• noun An organ stop that produces tones an octave above those usually produced by the keys played.
• noun The interval between any two frequencies having a ratio of 2 to 1.
• noun The eighth day after a feast day, counting the feast day as one.
• noun The entire period between a feast day and the eighth day following it.
• noun A group or series of eight.
• noun A group of eight lines of poetry, especially the first eight lines of a Petrarchan sonnet.
• noun A poem or stanza containing eight lines.
• noun Sports A rotating parry in fencing.

from The Century Dictionary.

• To play in octaves.
• In pianoforte- and harpsichordmaking, to reinforce the tone of a digital by adding a string tuned an octave above the usual tone of the digital.
• noun In fencing, the eighth guard: point low, hand moving to the right.
• In music, noting a tone, note, instrument, organ-stop, etc., whose pitch is an octave above the ordinary pitch or any pitch taken for reference: as, the piccolo is an octave flute.
• noun The eighth day from a festival, the feast-day itself being counted as the first: as, Low Sunday is the octave of Easter. The octave necessarily falls on the same day of the week as the feast from which it is counted.
• noun The prolongation of a festival till the eighth day inclusive; a period consisting of a feastday and the seven days following: as, St. John the Evangelist's day (December 27th) is within the octave of Christmas. See outas.
• noun In music: A tone on the eighth diatonic degree above or below a given tone; the next higher or lower replicate of a given tone.
• noun The interval between any tone and a tone on the eighth degree above or below it.
• noun The harmonic combination of two tones at the interval thus described.
• noun In a scale, the eighth tone from the bottom, or, more exactly, the tone with which the repetition of the scale begins; the upper key-note or tonic; the eighth: solmizated do, like the lower key-note.
• noun In a standard system of tones selected for artistic use, a division or section or group of tones an octave long, the limits of which are fixed by reference to a given or assumed standard tone whose exact pitch may be defined.
• noun In organ-building, a stop whose pipes give tones an octave above the normal pitch of the digitals used; specifically, such a stop of the diapason variety. Also known as the principal. Also called octave-flute, octavestop.
• noun Any interval resembling the musical octave in having the vibration-ratio of 1:2.
• noun Specifically, in versification: A stanza of eight lines; especially, the ottava rima (which see).
• noun The first two quatrains or eight lines in a sonnet. See sonnet.
• noun A small cask of wine containing the eighth part of a pipe.
• Consisting of eight; specifically, consisting of eight lines.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Consisting of eight; eight.
• noun The eighth day after a church festival, the festival day being included; also, the week following a church festival.
• noun The eighth tone in the scale; the interval between one and eight of the scale, or any interval of equal length; an interval of five tones and two semitones.
• noun The whole diatonic scale itself.
• noun (Poet.) The first two stanzas of a sonnet, consisting of four verses each; a stanza of eight lines.
• noun (Mus.) See under Double.
• noun (Mus.) a small flute, the tones of which range an octave higher than those of the German or ordinary flute; -- called also piccolo. See Piccolo.
• noun A small cask of wine, the eighth part of a pipe.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun music An interval of twelve semitones spanning eight degrees of the diatonic scale, representing a doubling or halving in pitch.
• noun music The pitch an octave higher than a given pitch.
• noun poetry A poetic stanza consisting of eight lines; usually used as one part of a sonnet.
• noun fencing The eighth defensive position, with the sword hand held at waist height, and the tip of the sword out straight at knee level.
• noun Christianity The day that is one week after a feast day in the Latin Rite of the Catholic Church.
• noun Christianity An eight day period beginning on a feast day in the Latin Rite of the Catholic Church.
• adjective obsolete Consisting of eight; eight in number.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a feast day and the seven days following it