obdurate
stubbornly persistent in wrongdoing
obeisance
bending the head or body or knee as a sign of reverence or submission or shame or greeting
obelisk
a stone pillar having a rectangular cross section tapering towards a pyramidal top
obsequious
attempting to win favor from influential people by flattery
obstreperous
noisily and stubbornly defiant
obtuse
of an angle; between 90 and 180 degrees
occident
the hemisphere that includes North America and South America
odium
hate coupled with disgust
odyssey
a long wandering and eventful journey
officious
intrusive in a meddling or offensive manner
olfactory
of or relating to olfaction
ominous
threatening or foreshadowing evil or tragic developments
onerous
not easily borne; wearing
opalescent
having a play of lustrous rainbow colors
opiate
a narcotic drug that contains opium or an opium derivative
opus
a musical work that has been created
opprobrium
a state of extreme dishonor
ordain
invest with ministerial or priestly authority
ordinate
the value of a coordinate on the vertical axis
ornate
marked by elaborate rhetoric and elaborated with decorative details
ornithologist
a zoologist who studies birds
orthography
a method of representing the sounds of a language by written or printed symbols
osseous
composed of or containing bone
ostensible
appearing as such but not necessarily so
ostentatious
intended to attract notice and impress others
ostracize
expel from a community or group
outlandish
conspicuously or grossly unconventional or unusual
overt
open and observable; not secret or hidden
