This section is from the book "Hill's Manual Of Social And Business Forms: A Guide To Correct Writing", by Thos. E. Hill. Also available from Amazon: Hill's Manual Of Social And Business Forms: The How-To-Do-Everything Book Of Victorian America.
Obvious - plain, apparent, open, clear, evident, visible, manifest.
Occupation - work, profession, calling, trade, business, avocation, employment.
Occupy - keep, hold, use, possess.
Occurrence - event, contingency, adventure, incident.
Odor - smell, fragrance, perfume, scent.
Offense - trespass, crime, injury, sin, outrage, insult, misdeed, wrong, transgression.
Offensive - mean, abusive, insulting, impertinent, insolent, rude, scurrilous, obnoxious, opprobrious.
Officious - busy, active, forward, obtrusive, intrusive. Only - solely, singly, alone, simply, merely.
Open - unravel, reveal, disclose, unlock.
Opening - fissure, aperture, hole, cavity.
Operation - performance, action, agency.
Opinion - belief, idea, sentiment, notion.
Opinionated - obstinate, stub-born, stiff, egotistical, conceited, self-willed.
Opponent - opposer, adversary, toe, enemy, antagonist.
Opposite - contrary, repugnant, adverse.
Opprobrious - reproachful, insolent, abusive, offensive, insulting, scandalous, scurrilous.
Opprobrium - shame, disgrace, reproach, infamy, ignominy.
Oration - speech, sermon, lecture, discourse, address, harangue.
Ordain - appoint, invest, order, prescribe.
Order - brotherhood, fraternity, rank, method, succession, series, degree, genus.
Order - mandate, injunction, precept, command.
Orderly - precise, regular, systematic, methodical.
Ordinary - usual, common.
Origin - rise, cause, source, foundation, beginning, descent, fountain.
Original - primitive, first, pristine, primary.
Ornament - decorate, beautify, adorn, deck, embellish.
Ornate - decorated, adorned, embellished, bedecked, garnished.
Ostentation - parade, show, display, boast.
Outrage - insult, injure, affront, violence.
Outward - extraneous, apparent, intrinsic.
Overbearing: - repressive, impertinent, haughty, lordly.
Overcome - vanquish, conquer, surmount, subdue. Overflow - fill, inundate, deluge, abound.
Overnight - mistake, error, misapprehension, inattention.
Overwhelm - overpower, crush, upturn, overthrow, subdue.
Owner - holder, proprietor, master, possessor.
Pacify - calm, still, quiet, soothe, conciliate.
Pain - distress, afflict, torture, torment, suffer, hurt.
Paint - portray, represent, depict, sketch, color, describe, delineate.
Pair - join, two, couple, brace.
Pale - fade, wan, white, pallid, fair.
Palpable - gross, plain, apparent, discernible, perceptible.
Palpitate - tremble, throb, beat, flutter, gasp, pant.
Pang - torture, torment, distress, agony, anguish, sorrow.
Pardon - acquit, forgive, clear, free, discharge, release, remit.
Parsimonious - mean, frugal, miserly, avaricious, penurious, niggardly.
Part - share, portion, division, piece, action.
Particular - individual, specific, exact. appropriate, circumstantial, peculiar, exclusive, punctual, distinct.
Particularly - chiefly, mainly, principally, especially, distinctly, specifically.
Partisan - disciple, adherent, follower.
Partner - associate, accomplice, colleague, coadjutor.
Passion - desire, feeling, love, anger, excitement.
Passionate - hot, angry, irascible, hasty, excitable.
Passive - submissive, unresisting, patient, resigned.
Pathetic - affecting, touching, moving.
Patience - endurance, fortitude, resignation.
Patient - resigned, composed, enduring, calm, passive, an invalid.
Peaceable - quiet, calm, serene, tranquil, mild, gentle.
Peevish - fretful, disagreeable, petulant, cross, captious, irritable.
Penalty - punishment, pain, fine, forfeiture, chastisement.
Penitence - contrition, remorse, compunction, repentance.
Penurious - parsimonious, sparing, miserly, niggardly, beggarly.
Penury - want, poverty, distress, indigence, need.
Perceive - observe, discern, distinguish.
Perception - belief, conception, sentiment, idea, sensation, notion.
Peremptory - positive, despotic, arbitrary, dogmatical, absolute.
Perfect - done, complete, finished. Perfidious - false, treacherous, faithless.
Perforate - pierce, bore, penetrate.
Perform - execute, accomplish, effect, produce, achieye, fulfill.
Perfume - odor, smell, scent, exhalation, fragrance.
Period - circuit, date, age, epoch, era. Permit - allow, suffer, consent, admit, tolerate, yield.
Pernicious - noisome, ruinous, destructive, mischievous, hurtful, noxious.
Perpetual - uninterrupted, incessant, unceasing, constant, continual.
Perplex - bewilder, annoy, confuse, involve, molest, puzzle, embarrass, harass, entangle.
Persevere - endure, continue, persist, insist, pursue, prosecute.
Perspicuity - clearness, transparency, brilliancy.
Persuade - urge, induce, exhort, influence, entice, prevail upon.
Perverse - stubborn, untractable, unmanageable, crooked, cross.
Pestilential - destructive, mischievous, epidemical, infectious, contagious.
Petition - prayer, supplication, request, suit, entreaty.
Picture - likeness, image, effigy, representation.
Pious - spiritual, devout, godly, religious.
Pique - offense, grudge, dislike, malice, spite, rancor.
Pity - sympathy, commiseration, compassion, condolence, mercy.
Place - site, ground, post, position.
Placid - still, calm, gentle, quiet, tranquil, serene.
Plague - perplex, embarrass, tantalize, annoy, importune, vex, torment.
Plain - perceptible, discernible, manifest, obvious, clear, apparent, evident, distinct.
Plan - design, contrivance, device, scheme, arrangement, project, stratagem. Pleasant - cheerful, jocular, gay, vivacious, agreeable, facetious, witty.
Please - gratify, satisfy, humor, delight.
Pleasure - satisfaction, delight, happiness, enjoyment, joy.