obsequious too eager to obey or serve

officious too eager or ready to help, offer advice

opprobrious showing scorn or reproach

ostentation display to obtain admiration or envy

ostentatious fond of

ostracism shut out from society, refuse to meet, talk

ostrich fast-running bird unable to fly

outset start

overhaul examine thoroughly to learn about the condition

overwhelm weigh down, submerge