English Words Starting With O

• observe

  verbverb-intransitiveverb-transitiveC1
  /əbˈzɜːv/to watch carefully, notice, or perceive; to remark or comment; to comply with a rule, law, or custom.
• observer

  nounB2
  /əbˈzɜːvə(r)/a person who watches or notices something, especially as a formal role
• obsess

  verbverb-intransitiveverb-transitiveB2
  /əbˈsɛs/To preoccupy or fill the mind continually and to a troubling extent.
• obsession

  nounB2
  /əbˈseʃ.ən/A state in which someone thinks about something or someone constantly in a way that is not normal or healthy; a persistent, disturbing preoccupation with an idea, feeling, or object.
• obsessive

  adjectivenounB2
  /əbˈsɛsɪv/Relating to a persistent, overwhelming, and often distressing preoccupation with a specific thought, idea, or activity.
• obsessive-compulsive

  adjectivenounC1
  /əbˌses.ɪv.kəmˈpʌl.sɪv/Relating to or characterised by a mental condition involving persistent, unwanted thoughts (obsessions) and repetitive behaviours or mental acts (compulsions).
• obsessive-compulsive disorder

  nounC1
  /əbˌses.ɪv kəmˌpʌl.sɪv dɪsˈɔː.dər/A mental health condition characterized by persistent, unwanted thoughts (obsessions) and repetitive behaviours or mental acts (compulsions) that an individual feels driven to perform.
• obsidian

  nounC1
  /əbˈsɪdɪən/A hard, dark, glassy volcanic rock, formed from quickly cooled lava.
• obsidian dating

  nounVery Low
  /əbˌsɪd.i.ən ˈdeɪ.tɪŋ/A scientific method used in archaeology to determine the age of obsidian artifacts by measuring the thickness of their hydration layer.
• obsidianite

  nounVery Low / Obscure
  /ˌɒb.sɪˈdɪə.naɪt/A person who is fanatically devoted to or an expert on the 1986 fantasy film 'Legend', directed by Ridley Scott.
• obsidional coin

  nounVery Low
  /əbˈsɪdɪənəl kɔɪn/A coin, typically of crude design and manufacture, minted urgently during a siege from available metals.
• obsolesce

  verbverb-intransitiveLow
  /ˌɒbsəˈlɛs/To fall into disuse; to become obsolete.
• obsolescence

  nounC1-C2
  /ˌɒbsəˈlesəns/The process or state of falling into disuse or becoming outdated.
• obsolete

  adjectiveverb-transitiveC1
  /ˌɒbsəˈliːt/No longer produced or used; out of date.
• obstacle

  nounB1
  /ˈɒb.stə.kəl/A physical object, situation, or condition that blocks or hinders progress or movement.
• obstacle course

  nounB1
  /ˈɒbstək(ə)l kɔːs/A path or area filled with physical barriers that must be overcome, typically as a challenge, test, or training exercise.
• obstacle race

  nounC1
  /ˈɒb.stə.kəl ˌreɪs/A physical competition in which participants must navigate through a series of physical obstacles.
• obstetrician

  nounC1
  /ˌɒb.stəˈtrɪʃ.ən/A medical doctor who specialises in pregnancy, childbirth, and the postpartum period, including the care of both the mother and the newborn.
• obstetrics

  nounC1-C2
  /əbˈstɛtrɪks/The branch of medicine that deals with childbirth and the care of women before, during, and after pregnancy.
• obstinacy

  nounC1
  /ˈɒb.stɪ.nə.si/the quality of being unreasonably determined to do something or hold a particular opinion, despite attempts to persuade or reason otherwise.

Showing 221–240 of 3187 words.