noun

• Abbreviation of October. [The tenth month of the Gregorian calendar, following September and preceding November. Abbreviation: Oct.]
• (computing, informal) Abbreviation of octal. [(arithmetic, computing, uncountable) The number system that uses the eight digits 0, 1, 2, 3, 4, 5, 6, 7.]
• (medicine) Initialism of optical coherence tomography: an optical signal acquisition and processing method that captures high-resolution three-dimensional images from biological tissues.