O O /ˈoʊ/

interjection

1. () Exclamations often denoting astonishment or unexpected discovery.  ( marry [Archaic] , od [Archaic] , holy crap [Vulgar] , Christ [Informal] , Christmas [Informal] , fancy [Informal, British] , god , Holy-dooly [Informal, Australian] , holy shit [Vulgar] , goodness [Informal] , gracious [Informal] , heavens [Informal] , Jesus [Informal] , Lord [Informal] , O , oh , ah , bejeezus [Informal, N. American] , bejesus [Informal, N. American] , blimey [Informal, British] , blooming heck [Informal, British] , blow me [Informal, British] , by George [Informal] , by Jove [Informal] , cor [Informal, British] , cor blimey [Informal, British] , crikey [Informal, British] , cripes [Informal] , crumbs [Informal, British] , fancy that [Informal] , gawd [Informal] , geez [Informal] , golly [Informal] , good grief [Informal] , good heavens [Informal] , goodness me [Informal] , gorblimey [Informal, British] , Gordon Bennett [Informal] , gosh [Informal] , gracious me [Informal] , heck [Informal] , holy cow [Informal] , holy mackerel [Informal] , holy moley [Informal] , holy moly [Informal] , holy smoke [Informal] , I'll be blowed [Informal, British] , jeepers [Informal] , jeepers creepers [Informal] , jeez [Informal] , Lordy [Informal] , my [Informal] , my goodness [Informal] , my word , oh boy [Informal] , strewth [Informal, British] , struth [Informal, British] , well I never [Informal] , yikes [Informal] )
   Exclamations often denoting astonishment or unexpected discovery.
   

noun

1. () A nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust  ( atomic number 8 , O , oxygen )
   a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
     Oxygen is necessary for the process of respiration in living organisms.
   Oxygen is necessary for the process of respiration in living organisms.
   
   
2. The blood group whose red cells carry neither the A nor B antigens  ( group O , O , type O )
   the blood group whose red cells carry neither the A nor B antigens
    People with type O blood are universal donors
   people with type O blood are universal donors
   
3. The 15th letter of the Roman alphabet  ( O )
   the 15th letter of the Roman alphabet