Outset
Origin
A word meaning to leave out which begins with an "o" is omit.
origin.
another word for chasm that begins with o omission opening oversight
owlish
overjoyed
overwhelmingoverwroughtoutstanding
Offend is a synonym for the word hurt. It begins with the letter O.
odd
Overwhelming is a synonym for awesome. It begins with O.
orderoveroutfitofficer
ovine
outdo