notorious :: outstandingly bad; unfavorably known
noxious :: harmful
nugatory :: futile; worthless
nutrient :: providing nourishment
obdurate :: stubborn
obese :: fat
oblique :: slanting; deviating from the perpendicular or from a straight line
obnoxious :: offensive
obsequious :: slavishly attentive; servile; sycophantic
obsolete :: outmoded
obtrusive :: pushing toward
obtuse :: blunt; stupid
occult :: mysterious; secret; supernatural
odious :: hateful
odoriferous :: giving off an order
odorous :: having an odor
officious :: meddlesome; excessively trying to please
olfactory :: concerning the sense of smell
ominous :: threatening
omnipotent :: all-powerful
omniscient :: all-knowing
omnivorous :: eating both plant and animal food; devouring everything
onerous :: burdensome
opalescent :: iridescent
opaque :: dark; not transparent
opportune :: timely; well chosen
opprobrious :: disgraceful
ornate :: excessively decorated; highly decorated
ostensible :: apparent; professed; pretended
ostentatious :: showy; pretentious
overt :: open to view
palatable :: agreeable; pleasing to the taste
palatial :: magnificent
pallid :: pale; wan
palpable :: tangible; easily perceptible
paltry :: insignificant; petty
parsimonious :: stingy; excessively frugal
passive :: not active; acted upon
pastoral :: rural
patent :: open for the public to read; obvious
pathetic :: causing sadness, compassion, pity; touching
pecuniary :: pertaining to money
pedantic :: showing off learning; bookish
pell-mell :: in confusion; disorderly
pellucid :: transparent; limpid; easy to understand
pendant :: hanging down from something
pendent :: suspended; jutting; pending
penitent :: repentant
pensive :: dreamily thoughtful; thoughtful with a hint of sadness
penurious :: stingy; parsimonious
peremptory :: demanding and leaving no choice
perennial :: lasting
perfidious :: basely false
perforce :: of necessity
perfunctory :: superficial; listless; not thorough
peripatetic :: walking about; moving
permeable :: porous; allowing passage through
pernicious :: very destructive
perpetual :: everlasting
perspicacious :: having insight; penetrating; astute