object, n. thing, article; goal, purpose, aim, motive, intent, design, target, butt, destination, view.

objection, n. exception, scruple, demurrer, cavil.  Antonyms:  approval, acquiescence.

objectionable, a. exceptionable, offensive, obnoxious, undesirable, displeasing.

objectless, a. aimless, desultory, purposeless, vague.

obligation, n. accountableness, responsibility, incumbency, duty, indebtedness; agreement, contract, stipulation, covenant, bond.

obligatory, a. binding, incumbent, imperative, coercive.  Antonyms:  optional, discretional.

oblige, v. constrain, obligate; please, gratify, accommodate, coerce, compel, necessitate, force.

obliging, a. complaisant, gracious, accommodating, affable, debonair, deferential, yielding.

obliterate, v. efface, erase, blot out, remove, destroy, expunge.

obliteration, n. extinction, erasure, effacement, removal.

oblivious, a. unmindful, unconscious, forgetful, heedless, disregardful.

obnoxious, a. subject, liable; offensive, odious, hateful, displeasing.

obscene, a. smutty, lewd, gross, indecent, immodest, indelicate, ribald.

obscenity, n. lewdness, smut, ribaldry, indecency, bawdiness, immodesty.

obscure, a. abstruse, vague, recondite, indefinite, ambiguous; humble, inglorious, mean, undistinguished; secluded, retired, remote; shaded, darkened.

obscure, v. darken, obfuscate, bedim, eclipse; involve, dissemble, disguise, confuse.

obscuring, n. obscuration, obscurity.

obscurity, n. ambiguity, vagueness; privacy, seclusion, retirement; darkness, obfuscation, obscuration.

obsequious, a. sycophantic, cringing, fawning, deferential, servile.

obsequiousness, n. sycophancy.

obsolete, a. disused, archaic, antiquated, unfashionable, old-fashioned.

obstacle, n. obstruction, barrier, impediment, hindrance, stumbling-block.

obstetrician, n. midwife, accoucheur.

obstetrics, n. tocology, midwifery.

obstinacy, n. incompliance, doggedness, perversity, obduracy, intractability, stubbornness.

obstinate, a. incompliant, intractable, mulish, perverse, dogged, contumacious, stubborn.  Antonyms:  amenable, yielding, tractable, submissive, compliant, obedient.

obstreperous, a. clamorous, vociferous, noisy, uproarious, boisterous.

obstruct, v. impede, oppose, retard, barricade, blockade, clog, interrupt, bar, restrain.

obstruction, n. obstacle, impediment, barrier, blockade, restraint.

obtain, v. gain, get, procure, acquire, win, attain, secure.

obtainable, a. procurable, attainable, accessible.  Antonyms:  unobtainable, unprocurable, unattainable, inaccessible.

obtrusive, a. officious, meddlesome, intrusive, forward.  Antonyms:  inobtrusive, retiring.