English Words Starting With O

• osmanli

  adjectivenounVery Low
  /ɒzˈmɑːnli/Relating to the Ottoman Empire or its people, culture, or language.
• osmeterium

  nounVery Low
  /ˌɒzmɪˈtɪərɪəm/A forked, fleshy, retractable organ found in the larvae (caterpillars) of swallowtail butterflies, which emits a strong-smelling chemical secretion as a defense mechanism against predators.
• osmics

  nounExtremely Rare
  /ˈɒzmɪks/The scientific study of smells and olfaction.
• osmidrosis

  nounVery low
  /ˌɒzmɪˈdrəʊsɪs/Foul-smelling sweat; a medical condition characterized by abnormally malodorous perspiration.
• osmiridium

  nounVery Low
  /ˌɒzmɪˈrɪdɪəm/A hard, dense, naturally occurring alloy of osmium and iridium.
• osmium

  nounC2
  /ˈɒzmiəm/A very hard, brittle, bluish-white transition metal in the platinum group, with the chemical symbol Os and atomic number 76.
• osmium tetroxide

  nounVery Low
  /ˈɒzmiəm tɛˈtrɒksaɪd/A highly toxic, volatile chemical compound (OsO₄) used primarily as a stain in electron microscopy and in certain organic synthesis reactions.
• osmometer

  nounRare
  /ɒzˈmɒm.ɪ.tə/A scientific instrument for measuring osmotic pressure.
• osmometry

  nounVery Low
  /ɒzˈmɒm.ɪ.tri/The measurement of osmotic pressure.
• osmoregulation

  nounC2
  /ˌɒzməʊˌrɛɡjʊˈleɪʃ(ə)n/The physiological process by which an organism maintains a constant internal concentration of water and dissolved salts (osmotic pressure), regardless of the external environment.
• osmose

  nounverbverb-intransitiveverb-transitiveRare (C2)
  /ˈɒz.məʊz/to undergo osmosis; to pass gradually by or as if by osmosis from one substance, region, or condition to another
• osmosis

  nounC1
  /ɒzˈməʊ.sɪs/A scientific process in which molecules of a solvent (typically water) pass through a semi-permeable membrane from a less concentrated solution into a more concentrated one, equalizing the concentrations on each side.
• osmotic pressure

  nounLow
  /ɒzˈmɒt.ɪk ˈpreʃ.ər/The minimum pressure that must be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
• osmund

  nounC2
  /ˈɒzmənd/A type of large, coarse fern of the genus Osmunda, especially the royal fern (Osmunda regalis).
• osmunda

  nounRare / Specialised
  /ɒzˈmʌndə/A genus of large, coarse, terrestrial ferns, typically found in moist habitats.
• osnabruck

  nounRare (as a common noun or topic outside of geographical/historical contexts)
  /ˈɒznəbrʊk/A city in northwestern Germany, in the state of Lower Saxony.
• osnaburg

  nounLow
  /ˈɒznəbɜːɡ/A coarse, strong, plain-woven cotton fabric, originally made of flax and tow, now often used for industrial purposes or rustic clothing.
• osorno

  nounVery Low
  /ɒˈsɔːnəʊ/A proper noun referring primarily to a city and province in southern Chile, located in the Los Lagos Region.
• osprey

  nounC1
  /ˈɒspreɪ/A large fish-eating bird of prey (Pandion haliaetus) with a white head and underparts, found worldwide near coastlines and inland waters.
• ossa

  nounC2/Rare
  /ˈɒsə/The plural of 'os', a medical/formal term for a bone.

Showing 2181–2200 of 3187 words.