English Words Starting With O

• octobrist

  nounC2
  /ɒkˈtəʊ.brɪst/A member of a political party in early 20th-century Russia.
• octocentenary

  adjectivenounExtremely Rare / Technical
  /ˌɒktə(ʊ)sɛnˈtiːn(ə)ri/An eight-hundredth anniversary; the celebration of something that happened 800 years ago.
• octodecillion

  adjectivenounVery Rare
  /ˌɒktəʊdɪˈsɪlɪən/A cardinal number represented by 1 followed by either 57 or 108 zeros, depending on the naming system used.
• octodecimo

  adjectivenounRare / Obsolete
  /ˌɒktə(ʊ)ˈdɛsɪməʊ/A book size where each leaf is one eighteenth the size of the original printing sheet.
• octofoil

  nounC2
  /ˈɒktə(ʊ)fɔɪl/A stylized design or shape, typically heraldic or architectural, consisting of eight symmetrical lobes or leaves arranged around a central point.
• octogenarian

  adjectivenounC1
  /ˌɒk.tə.dʒəˈneə.ri.ən/A person who is between 80 and 89 years old.
• octometer

  nounRare
  /ɒkˈtɒmɪtə/A poetic metre consisting of eight metrical feet per line.
• octonary

  adjectivenounVery Rare
  /ˈɒktən(ə)ri/Related to or consisting of eight; a group or set of eight.
• octopod

  adjectivenounLow
  /ˈɒktəpɒd/A member of the order Octopoda, a type of cephalopod mollusc characterised by eight arms, such as an octopus.
• octopus

  nounB1
  /ˈɒk.tə.pəs/A sea animal with a soft, oval body and eight long tentacles (arms), known for its intelligence and ability to change colour.
• octoroon

  nounObsolete/Historical/Offensive
  /ˌɒk.təˈruːn/A dated, offensive term historically used in some parts of the world, especially the United States, to classify a person as having one-eighth Black ancestry.
• octosyllabic

  adjectivenounC1
  /ˌɒktəʊsɪˈlabɪk/Consisting of or using lines or words of eight syllables.
• octosyllable

  nounLow
  /ˌɒktə(ʊ)ˈsɪləbl/A word or line of verse consisting of eight syllables.
• octothorpe

  nounC2
  /ˈɒktəʊθɔːp/The symbol #.
• octroi

  nounVery low (archaic/technical)
  /ˈɒktrwɑː/A local tax or duty levied on goods brought into a town or city, especially on food or household goods, for consumption within that municipality.
• octuple

  adjectivenounverbverb-transitiveC2/Rare
  /ɒkˈtjuːp(ə)l/To multiply something by eight; or eight times as great in size, amount, or number.
• octuplet

  nounC2
  /ˈɒktjʊplət/A group or set of eight, especially eight children born from a single pregnancy.
• octuplicate

  adjectivenounverb-transitiveC1
  /ɒkˈtjuːplɪkeɪt/To produce eight identical copies or sets of something.
• octyl alcohol

  nounC2
  /ˈɒktɪl ˈælkəhɒl/A primary alcohol with eight carbon atoms in its alkyl chain, specifically 1-octanol.
• octyl phenol

  nounVery Low / Technical
  /ˈɒktɪl ˈfiːnɒl/A synthetic organic chemical compound consisting of an octyl hydrocarbon chain attached to a phenol group.

Showing 401–420 of 3187 words.