1. obstacle race a race in which competitors must negotiate obstacles
  2. obstacle something that stands in the way and must be surmounted
  3. abstract existing only in the mind
  4. obstreperous noisily and stubbornly defiant
  5. bicycle race a race between people riding bicycles
  6. abstruse difficult to understand
  7. obstinate marked by tenacious unwillingness to yield
  8. abstinence the trait of refraining from something, especially alcohol
  9. stake race a horse race in which part of the prize is put up by the owners of the horses in the race
  10. obstetrics the branch of medicine dealing with childbirth and care of the mother
  11. obstetric of or relating to or used in or practicing obstetrics
  12. obstinacy resolute adherence to your own ideas or desires
  13. upstager a selfish actor who upstages the other actors
  14. particularize be specific about
  15. obstinance resolute adherence to your own ideas or desires
  16. particularise be specific about
  17. abstract art an abstract genre of art
  18. Roystonea oleracea West Indian palm with leaf buds that are edible when young
  19. upstairs on a floor above
  20. upset price (auction) the minimum price at which a seller of property will entertain bids