English Words Starting With O

• oppositionist

  nounC2
  /ˌɒpəˈzɪʃ(ə)nɪst/A person who opposes or is a member of an opposition, especially in politics.
• oppress

  verbverb-transitiveC1
  /əˈprɛs/To keep someone in subjugation and hardship, especially by the unjust exercise of authority.
• oppressed

  adjectivenounverbB2
  /əˈprɛst/Subjected to unjust or cruel control and power; burdened harshly.
• oppression

  nounC1
  /əˈpreʃ.ən/The state of being subjected to unjust and cruel exercise of authority or power.
• oppressor

  nounC1/C2
  /əˈpres.ər/A person, group, or authority that rules over others in a cruel, unjust, and tyrannical manner.
• opprobrium

  nounC1/C2
  /əˈprəʊbrɪəm/harsh criticism or public disgrace resulting from shameful or outrageous conduct.
• oppugn

  verbverb-transitiveVery Low / Archaic
  /ɒˈpjuːn/To argue against or challenge something strongly; to dispute or call into question.
• opry

  nounRare (C2)
  /ˈɒp.ri/A specific style of traditional country music and its associated variety show, originating in the US, particularly the weekly 'Grand Ole Opry' radio broadcast.
• ops

  nounLow
  /ɒps/An informal, clipped plural form of 'operations', most commonly referring to military or technical operations.
• opsimath

  nounRare
  /ˈɒpsɪmaθ/A person who begins to learn or study late in life.
• opsin

  nounC2
  /ˈɒpsɪn/A protein that combines with a light-sensitive pigment (retinal) to form visual pigments (rhodopsin, photopsin) in the photoreceptor cells of the retina.
• opsonic index

  nounVery Low
  /ɒpˈsɒnɪk ˈɪndɛks/A numerical measure of the capacity of blood serum to enhance phagocytosis of a specific microorganism, indicating immune response strength.
• opsonify

  verb-transitiveRare/Highly Technical
  /ɒpˈsɒnɪfaɪ/To make bacteria or other cells more susceptible to phagocytosis by coating them with opsonins (antibodies or complement proteins).
• opsonin

  nounC2 (Specialized Scientific/Medical)
  /ˈɒpsənɪn/An antibody or other blood serum component that binds to pathogens, making them more susceptible to phagocytosis (engulfment and destruction) by white blood cells.
• opsonize

  verbverb-transitiveC2
  /ˈɒpsənaɪz/To make a microorganism more susceptible to phagocytosis by coating it with antibodies or other proteins.
• opt

  verbverb-intransitiveB2
  /ɒpt/To make a choice or decision from a range of possibilities.
• opt in

  verbC1
  /ˌɒpt ˈɪn/To choose to participate in or be included in something, especially a system, scheme, or mailing list.
• opt out

  nounverbB2
  /ˌɒpt ˈaʊt/to choose not to be involved in or part of a system, agreement, or activity.
• optative

  adjectivenounC2
  /ˈɒp.tə.tɪv/Relating to or expressing a wish or desire.
• opted

  verbHigh (B1-B2)
  /ˈɒptɪd/The past tense of 'opt', meaning to have made a choice from a set of alternatives.

Showing 1541–1560 of 3187 words.