| octane number |
a number that designates the antiknock properties of a gasoline, based on the percentage of isooctane in it; octane rating. |
| octane rating |
see "octane number." |
| octant |
an eighth of a circle, or the arc or area it includes. [4 definitions] |
| octave |
a musical tone eight full tones above or below another tone, with twice or half as many vibrations per second as the other tone. [5 definitions] |
| octavo |
a page or book size resulting from folding a printer's sheet of paper into eight leaves, each about six inches by nine inches. |
| octet |
a group of eight singers or musicians. [3 definitions] |
| octillion |
the number represented by the Arabic numeral 1027. [2 definitions] |
| octo- |
eight. |
| October |
the tenth month of the Gregorian calendar year, having thirty-one days. |
| October Revolution |
see "Russian Revolution." |
| octogenarian |
being, of, or pertaining to one that is between eighty and ninety years old. [2 definitions] |
| octopus |
any of several related carnivorous sea animals with a soft, rounded body and eight long tentacles with two rows of suckers on each. [2 definitions] |
| octoroon |
a person whose ancestry is one eighth black. |
| octuple |
having or composed of eight parts. [3 definitions] |
| ocular |
of, pertaining to, or like the eye or eyes. [3 definitions] |
| oculist |
formerly, an ophthalmologist. [2 definitions] |
| oculomotor |
designating the nerves that supply the muscles that move each eyeball. |
| OD |
abbreviation of "overdose." |
| odalisque |
a female slave or concubine in a harem. |
| odd |
different from what is expected or customary; strange. [7 definitions] |
| oddball |
(informal) a person or thing that is unconventional or eccentric. [2 definitions] |