Another word for water that starts with the letter 'O' is oxygen dihydrogen.
ocean
Orator is another word for speaker.
originonset
Ogre, generally
Onus
other
Oh, I'm rich
it can i think the word starts with an o
outstanding i hope this helps B)
oblong.
oblong; such as an oval or rectangle
Ogre - as in Shrek
the word that starts with the letter o isonizalation glad to help