Form of octa- or octo- used before a vowel.

Alternative spelling of Oct.

Abbreviation of October.

(computing, informal) Abbreviation of octal.

(medicine) Initialism of optical coherence tomography: an optical signal acquisition and processing method that captures high-resolution three-dimensional images from biological tissues.

Initialism of One Country, Two Systems, the political structure by which Hong Kong and Macau are administered separately from mainland China. Chinese: 一國兩制／一国两制 (yī guó liǎng zhì).

The tenth month of the Gregorian calendar, following September and preceding November. Abbreviation: Oct. / (rare) A female given name from English.

(now historical) A type of ale traditionally brewed in October.

(historical, transitive) In the early Soviet Union, to give a child a name tinged with Soviet revolutionary thought, as opposed to religious christening.

Any of several marine molluscs of the family Octopodidae, having no internal or external protective shell or bone (unlike the nautilus, squid and cuttlefish) and eight arms each covered with suckers.