OBDURATE
hardened in feeling; resistant to persuasion
OBLIQUE
indirect or evasive; misleading or devious
OBSEQUIOUS
overly submissive and eager to please
OBSTINATE
stubborn; unyielding
OBVIATE
to prevent; to make unnecessary
OCCLUDE
to stop up; prevent the passage of
OFFICIOUS
too helpful; meddlesome
ONEROUS
troublesome and oppressive; burdensome
OPAQUE
impossible to see through; preventing the passage of light
OPINE
to express an opinion
OPPROBRIUM
public disgrace
OROTUND
pompous
OSSIFY
to change into bone; to become hardened or set in a rigidly conventional pattern
OSTENSIBLE
apparent
OSTENTATION
excessive showiness
OVERWROUGHT
agitated; overdone