worst

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

• adjective Most inferior, as in quality, condition, or effect.
• adjective Most severe or unfavorable.
• adjective Being furthest from an ideal or a standard; least desirable or satisfactory.
• adverb In the worst manner or degree.
• transitive verb To gain the advantage over; defeat.
• noun Something that is worst.
• idiom (at (the) worst) Under the most negative circumstances, estimation, or interpretation.
• idiom (get/have) To suffer a defeat or disadvantage.
• idiom (if (the) worst comes to (the) worst) If the very worst thing happens.
• idiom (in the worst way) Very much; a great deal.

from The Century Dictionary.

• In a manner or to a degree the extreme of bad or evil; most or least (according to the sense of the verb).
• The superlative of bad, evil, or ill; bad in the highest degree, whether morally, physically, financially, or otherwise: as, the worst sinner; the worst disease; the worst evil that can befall a state or an individual.
• noun That which is most evil or bad; the most bad, severe, aggravated, or calamitous thing, part, time, or state: usually with the: as, in the worst of the storm; to get the worst of a contest; to see a thing at its worst; to do one's worst.
• noun in the most evil, severe, or undesirable state; at the greatest disadvantage.
• To get the advantage over in a contest; defeat; overthrow.
• Synonyms To beat, discomfit, foil, overcome.
• To grow worse; deteriorate; worsen.

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

• intransitive verb rare To grow worse; to deteriorate.
• Bad, evil, or pernicious, in the highest degree, whether in a physical or moral sense. See worse.
• transitive verb To gain advantage over, in contest or competition; to get the better of; to defeat; to overthrow; to discomfit.
• noun That which is most bad or evil; the most severe, pernicious, calamitous, or wicked state or degree.

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

• adjective superlative form of bad: most bad.
• adverb In the worst way: most badly, most ill.
• verb archaic, transitive To make worse.
• verb dated, intransitive To grow worse; to deteriorate.
• verb rare To outdo or defeat, especially in battle.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective (superlative of `bad') most wanting in quality or value or condition
• noun the least favorable outcome
• adverb to the highest degree of inferiority or badness
• noun the weakest effort or poorest achievement one is capable of
• noun the greatest damage or wickedness of which one is capable
• verb defeat thoroughly