scrub

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To rub hard in order to clean.
• intransitive verb To remove (dirt or stains) by hard rubbing.
• intransitive verb To remove impurities from (a gas) chemically.
• intransitive verb Slang To cancel or abandon; drop.
• intransitive verb To clean or wash something by hard rubbing.
• noun The act or an instance of scrubbing.
• noun A preparation or product used in scrubbing.
• noun The articles of clothing that make up a scrub suit.
• noun Vegetation consisting chiefly of shrubs and small trees.
• noun An area covered with such vegetation.
• noun A domestic animal that is feral or not purebred.
• noun Slang A contemptible or incompetent person.
• noun Sports A player not on the varsity or first team.

from The Century Dictionary.

• noun A bush; shrub; a tree or shrub seemingly or really stunted.
• noun Collectively, bushes; brushwood; underwood; stunted forest.
• noun A worn-out brush; a stunted broom.
• noun One who labors hard and lives meanly; a drudge; a mean or common fellow.
• noun A worn-out or worthless horse, ox, or other animal, or one of a common or inferior breed.
• noun Anything small and mean.
• Of inferior breed or stunted growth; ill-conditioned; hence, scraggy; shabby; mean; scurvy; contemptible; small.
• To rub hard, either with a brush or other instrument or a cloth, or with the bare hand, for the purpose of cleaning, scouring, or making bright; cleanse, scour, or polish by rubbing with something rough.
• To cleanse, scour, or polish things by rubbing them with something rough or coarse; rub hard.
• To drudge; grub: as, to scrub hard for a living.
• noun A scrubbing.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To rub anything hard, especially with a wet brush; to scour; hence, to be diligent and penurious.
• transitive verb To rub hard; to wash with rubbing; usually, to rub with a wet brush, or with something coarse or rough, for the purpose of cleaning or brightening.
• adjective Mean; dirty; contemptible; scrubby.
• adjective a game, as of ball, by unpracticed players.
• adjective a race between scrubs, or between untrained animals or contestants.
• noun One who labors hard and lives meanly; a mean fellow.
• noun Something small and mean.
• noun A worn-out brush.
• noun A thicket or jungle, often specified by the name of the prevailing plant
• noun (Stock Breeding), U.S. One of the common live stock of a region of no particular breed or not of pure breed, esp. when inferior in size, etc.
• noun Australia & South Africa Vegetation of inferior quality, though sometimes thick and impenetrable, growing in poor soil or in sand; also, brush; -- called also scrub brush. See Brush, above.
• noun (Forestry) A low, straggling tree of inferior quality.
• noun (Zoöl.) an Australian passerine bird of the family Atrichornithidæ, as Atrichia clamosa; -- called also brush bird.
• noun (Bot.) the popular name of several dwarfish species of oak. The scrub oak of New England and the Middle States is Quercus ilicifolia, a scraggy shrub; that of the Southern States is a small tree (Q. Catesbæi); that of the Rocky Mountain region is Q. undulata, var. Gambelii.
• noun (Zoöl.) an Australian singing bird of the genus Drymodes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Mean; dirty; contemptible; scrubby.
• noun One who labors hard and lives meanly; a mean fellow.
• noun One who is a freak or unable to complete easy tasks.
• noun A thicket or jungle, often specified by the name of the prevailing plant; as, oak scrub, palmetto scrub, etc.
• noun US, stock breeding One of the common livestock of a region of no particular breed or not of pure breed, especially when inferior in size, etc. Often used to refer to male animals unsuited for breeding.
• noun Vegetation of inferior quality, though sometimes thick and impenetrable, growing in poor soil or in sand; also, brush.
• noun One not on the first team of players, a substitute.
• verb transitive To rub hard; to wash with rubbing; usually, to rub with a wet brush, or with something coarse or rough, for the purpose of cleaning or brightening; as, to scrub a floor, a doorplate.
• verb intransitive To rub anything hard, especially with a wet brush; to scour;