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150 Words Starting with “O” – Expand Your English Vocabulary

English Vocabulary

Here’s a list of 150 words starting with “O” along with their meanings. I’ve kept the meanings simple and clear:

  1. Oasis – A fertile area in a desert

  2. Obedient – Willing to follow orders

  3. Obese – Very overweight

  4. Obey – To follow instructions

  5. Obituary – A notice of someone’s death

  6. Objective – Goal or aim

  7. Oblige – To do a favor or help

  8. Obscure – Not clear or hard to understand

  9. Observe – To watch carefully

  10. Obstacle – Something that blocks progress

  11. Obtain – To get or acquire

  12. Obvious – Easy to see or understand

  13. Occasion – A special event or time

  14. Occupy – To take up space or time

  15. Ocean – Large body of saltwater

  16. Odd – Strange or unusual

  17. Odor – A smell

  18. Offend – To hurt someone’s feelings

  19. Offer – To present or give

  20. Office – Place where work is done

  21. Officer – A person in authority

  22. Official – Approved by authority

  23. Offset – To balance or counteract

  24. Often – Frequently

  25. Oil – A slippery liquid from plants or minerals

  26. Old – Not young; aged

  27. Olympic – Related to the Olympic Games

  28. Omit – To leave out

  29. Onion – A vegetable with layers

  30. Online – Connected to the internet

  31. Open – Not closed

  32. Operate – To work or control

  33. Opinion – A personal view

  34. Opponent – Rival or competitor

  35. Opportunity – A chance to do something

  36. Oppose – To be against

  37. Option – A choice

  38. Orange – A fruit or color

  39. Orbit – Path of a planet or object in space

  40. Order – An arrangement or command

  41. Ordinary – Normal or usual

  42. Organ – Part of a living body or musical instrument

  43. Organic – Natural, without chemicals

  44. Organize – To arrange systematically

  45. Origin – Beginning or source

  46. Original – First or new

  47. Ornament – Decoration

  48. Other – Different one

  49. Ounce – A unit of weight

  50. Outbreak – Sudden occurrence (like disease)

  51. Outcome – Result

  52. Outdoor – Outside, in the open air

  53. Outer – On the outside

  54. Outfit – Clothes worn together

  55. Outlaw – Criminal or banned person

  56. Outline – Main points or shape

  57. Output – Result of work or production

  58. Outstanding – Excellent or not finished

  59. Ovary – Female reproductive organ

  60. Overcome – To succeed after difficulty

  61. Overeat – To eat too much

  62. Overflow – Spill over

  63. Overlook – Fail to notice or have a view from above

  64. Overtake – To catch up or pass

  65. Overtime – Extra time beyond regular work

  66. Overwhelm – To overpower or crush

  67. Owner – Someone who possesses something

  68. Oxidize – To combine with oxygen

  69. Oxygen – Gas needed for breathing

  70. Oyster – A sea creature that produces pearls

  71. Objection – Expression of disapproval

  72. Obligation – Duty or responsibility

  73. Obsession – Extreme preoccupation

  74. Obsolete – No longer used

  75. Occur – To happen

  76. Occupation – Job or profession

  77. Octopus – Sea animal with eight arms

  78. Odyssey – Long adventurous journey

  79. Offense – Crime or insult

  80. Offerings – Gifts or sacrifices

  81. Officially – By authority

  82. Offsetting – Balancing effect

  83. Olive – A fruit or tree

  84. Ominous – Suggesting something bad will happen

  85. Oncoming – Approaching

  86. Onset – Start of something

  87. Operate – To control or perform surgery

  88. Opinionated – Stubborn about beliefs

  89. Opponent – Rival

  90. Opportunist – Someone who takes advantage of situations

  91. Optimism – Positive thinking

  92. Optimize – Make the best use of

  93. Optional – Not mandatory

  94. Oral – Related to the mouth or speaking

  95. Orator – Public speaker

  96. Orbiting – Moving around in a path

  97. Ordain – To officially appoint

  98. Orderly – Organized or neat

  99. Organic – Natural

  100. Organism – Living thing

  101. Orientation – Introduction or alignment

  102. Originality – Uniqueness

  103. Ornate – Highly decorated

  104. Orphan – Child without parents

  105. Oscillate – To swing back and forth

  106. Ostrich – Large flightless bird

  107. Outcome – Result

  108. Outrage – Extreme anger

  109. Outstanding – Remarkable

  110. Outskirts – Outer areas of a city

  111. Overboard – Off a ship into water

  112. Overcast – Cloudy

  113. Overcome – Conquer

  114. Overjoyed – Extremely happy

  115. Overlook – Miss noticing or have a view

  116. Overpower – Defeat completely

  117. Overrun – Spread over

  118. Oversee – Supervise

  119. Overseas – Across the sea

  120. Overtime – Extra hours

  121. Overwhelm – Crush or overpower

  122. Owe – To be indebted

  123. Own – To possess

  124. Ox – Male bovine animal

  125. Ozone – Protective layer in the atmosphere

  126. Oblique – Slanting, not direct

  127. Oblivion – State of being forgotten

  128. Obscenity – Offensive behavior or language

  129. Obscurity – Darkness or unknown

  130. Observant – Quick to notice

  131. Obsessional – Related to obsession

  132. Occult – Supernatural

  133. Occupational – Related to work

  134. Octagon – Eight-sided shape

  135. Oddity – Something strange

  136. Offshoot – Branch or offshoot from main

  137. Omnipotent – All-powerful

  138. Omniscient – All-knowing

  139. Onlooker – Bystander

  140. Onward – Forward

  141. Opalescent – Showing colors like an opal

  142. Opaque – Not transparent

  143. Oppression – Cruel treatment

  144. Optical – Related to vision

  145. Optimistic – Hopeful

  146. Orchestrate – Arrange carefully

  147. Ordination – Official appointment in religion

  148. Orifice – Opening or hole

  149. Outlast – Survive longer

  150. Outspoken – Frank in speech

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Hi, I’m Manoj! I’m an English teacher and soft skills trainer with over 10 years of experience. I love sharing simple lessons on vocabulary, grammar, and spoken English to make learning easy and enjoyable.

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