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.
Magnitude - size, greatness, bulk.
Maintain - sustain, keep, support, help, continue, assert, defend, vindicate.
Malady - evil, disease, affliction, disorder, distemper.
Manage - control, direct, conduct.
Mandate - command, charge, injunction, order.
Mangle - cut, lacerate, mutilate, tear, maim.
Manifest - evident, clear, open, apparent, obvious, plain.
Margin - edge, verge, rim, brim, brink, border.
Mark - stamp, impress, imprint, brand, show, observe.
Marriage - matrimony, wedlock, nuptials.
Marvel - wonder, prodigy, miracle.
Massive - large, heavy, bulky, ponderous.
Master - achieve, overcome, surmount, conquer.
Mature - perfect, complete, ripe.
Maxim - saying, adage, proverb.
Mean - abject, low, despicable, miserly, sordid, penurious, niggardly.
Meaning - sense, import, signification, intention, purpose, design.
Meanwhile - meantime, interim, intervening.
Mechanic - artisan, artificer.
Meddle - interpose, interfere, interrupt.
Mediate - intercede, interpose.
Meek - mild, soft, gentle, humble.
Meet - assemble, join, fit, becoming.
Meeting - assembly, company, auditory, congregation.
Melancholy - sadness, distress, depression, gloom, grief, dejection.
Melody - harmony, unison, happiness, concord.
Melt - dissolve, soften, liquefy.
Memory - remembrance, reminiscence, recollection.
Mend - improve, repair, rectify, correct.
Merciful - mild, tender, gracious, benignant, compassionate, forgiving.
Merciless - hard-hearted, pitiless, cruel, unmerciful.
Mercy - pity, clemency, compassion, lenity.
Merry - happy, joyous, cheerful, gay, lively, mirthful, sportive, sprightly, vivacious.
Messenger - bearer, carrier, harbinger, forerunner, precursor.
Metaphor - similitude, trope, emblem, allegory, symbol.
Method - order, manner, system, mode, rule, plan, regularity.
Mighty - strong, powerful,great, potent.
Mild - meek, gentle, kind, easy, sweet, tender, mellow.
Mindful - heedful, observant, attentive.
Minister - contribute, supply, administer.
Mirth - merriment, joy, hilarity, cheerfulness, vivacity, jollity.
Mischief - damage, harm, hurt, misfortune, injury.
Miserly - stingy, covetous, niggardly, penurious, avaricious.
Misfortune - calamity, harm, disaster, mishap, ill-luck.
Mistake - error, blunder, misconception.
Misuse - ill-treat, pervert, abuse, misapply.
Mitigate - lessen, alleviate, appease, ameliorate, abate, assuage, soothe, mollify.
Model - pattern, copy, sample, mould, specimen.
Moderation - temperance, sobriety, frugality, forbearance, modesty.
Modern - recent, late, new, novel.
Modest - quiet, retiring, reserved, diffident, bashful, unassuming.
Modify - re-arrange, change, extenuate, alter, moderate.
Molest - annoy, vex, tease, incommode, trouble, disturb.
Mollify - ease, appease, moderate, mitigate, assuage, soften.
Morose - sour, sillen, gloomy, peevish, forbidding.
Motive - incentive, reason, cause, principle. Mourn - grieve, lament, sorrow, bewail, bemoan.
Move - change, para, stir, incite, influence, persuade, actuate, instigate, impel.
Munificent - bounteous, bountiful, generous, beneficent, liberal, plentiful.
Muse - study, ponder, wonder, reflect, think, meditate, contemplate.
Mutable - changeable, unsteady, inconstant, fickle, wavering, unstable, variable, alterable, irresolute.
Mutilate - deface, injure, destroy, deprive, mangle, maim.
Mutinous - turbulent, seditious, insubordinate.
Mysterious - hidden, dim, dark obscure, mystic, latent.
Naked - exposed, nude, unclothed, uncovered, simple, plain.
Name - cognomen, appellation, title, reputation, credit, denomination.
Narrow - contracted, confined, limited, curtailed, close.
Native - indigenous, genuine, intrinsic.
Near - adjoining, adjacent, close, contiguous.
Necessary - needful, expedient, indispensable, essential, important, requisite.
Need - poverty, want, penury, indigence.
Nefarious - evil, wicked, unjust, wrong, iniquitous.
Negligent - careless, heedless, remiss, neglectful, inattentive.
New - fresh, late, modern, novel.
Nigh - close, adjoining, contiguous, near, adjacent.
Noble - distinguished, elevated, exalted, illustrious, great, grand.
Noisy - boisterous, turbulent, high, clamorous, loud sounding.
Noted - renowned, distinguished, conspicuous, celebrated, eminent, notorious, illustrious.
Notice - warning, information, intelligence, advice.
Notion - thought, opinion, sentiment, whim, idea, conception, perception.
Notorious - celebrated, renowned, distinguished, noted, public, conspicuous.
Notwithstanding - nevertheless, however, in spite of, yet.
Nourish - feed, uphold, maintain, cherish, nurture, support.
Obdurate - inflexible, unfeeling, callous, impenitent, hardened, in-sensible, obstinate.
Obedient - submissive, compliant, yielding, dutiful, obsequious, respectful.
Object - end, subject, aim.
Object - oppose, against, except to.
Oblige - compel, coerce, bind, engage, force, favor, please, gratify.
Obnoxious - offensive, liable, disagreeable, unpleasant, exposed.
Obscure - hidden, concealed, indistinct, difficult, dark, abstruse.
Observant - watchful, attentive, mindful, regardful.
Observe - see, notice, watch, follow, remark, keep.
Obsolete - disused, old, worn-out, antiquated, ancient, old-fashioned.
Obstacle - impediment, obstruction, difficulty, hinderance.
Obstinate - stubborn, resolute, headstrong.
Obstruct - impede, hinder, stop, prevent.
Obtain - gain, secure, get, win, acquire, procure, earn.