Definition of ostrog in US English:

ostrog

noun

historical
  • In Russia (especially in Siberia): a fortified house or village surrounded by a palisade or wall; a fort; a prison.

Origin

Mid 18th century; earliest use found in Philosophical Transactions of the Royal Society of London. From Russian ostrog from ostryj sharp from the same Indo-European base as Sanskrit aśri corner, aśani tip of a missile, ancient Greek ἄκρος tip, point, and forms in other Indo-European languages.