opposite

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

• adjective Placed or located directly across from something else or from each other.
• adjective Facing the other way; moving or tending away from each other.
• adjective Being the other of two complementary or mutually exclusive things.
• adjective Altogether different, as in nature, quality, or significance.
• adjective Sharply contrasting; antithetical.
• adjective Growing in pairs on either side of a stem.
• adjective Arranged on the same radius as another part, as stamens and petals.
• noun One that is opposite or contrary to another.
• noun An opponent or antagonist.
• noun An antonym.
• adverb In an opposite position.
• preposition Across from or facing.
• preposition In a complementary dramatic role to.

from The Century Dictionary.

• In gcom., in any complete set of connectors or fans, said of the first and the (n /2+l)th, when n is even.
• noun In geometry, an opposite point.
• That forms or is situated in or on the other or further side, end, or boundary of an interval, space, or thing; placed over against or face to face with (another or one another): literally or figuratively: as, the opposite side of the street or square; the opposite door; an opposite angle.
• Contrary; reverse.
• Of a totally or radically different nature, quality, or tendency; also (of two persons or things), mutually antagonistic or repugnant; mutually opposed in character or action; contradictory; non-congruent: as, words of opposite meaning; opposite terms.
• Adverse; opposed; hostile; antagonistic; inimical.
• In botany: Situated on opposite sides of an axis, as leaves when there are two on one node.
• Having a position between an organ and the axis on which it is borne, as a stamen when it is opposite a sepal or petal. In both senses opposed to alternate.
• noun One who opposes or is adverse; an opponent; an adversary; an enemy; an antagonist.
• noun That which opposes; that which is opposed or is opposite; a complement in characteristic qualities or properties; specifically, as a logical term, anything contrasted with another in any sense.
• noun [Some modern writers on logic wish to call any two different species of the same genus opposites. This practice has little to recommend it.]

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

• noun obsolete One who opposes; an opponent; an antagonist.
• noun That which is opposed or contrary in character or meaning.
• noun that which is conspicuously different in most important respects.
• adjective Placed over against; standing or situated over against or in front; facing; -- often with to.
• adjective Situated on the other end of an imaginary line passing through or near the middle of an intervening space or object; -- of one object with respect to another; -- also used both to describe two objects with respect to each other.
• adjective Applied to the other of two things which are entirely different; other
• adjective Extremely different; inconsistent; contrary; repugnant; antagonistic.
• adjective Set over against each other, but separated by the whole diameter of the stem, as two leaves at the same node.
• adjective Placed directly in front of another part or organ, as a stamen which stands before a petal.

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

• adjective Located directly across from something else, or from each other.
• adjective Facing in the other direction.
• adjective Of either of two complementary or mutually exclusive things.
• noun Something opposite or contrary to another.
• noun An opponent.
• noun An antonym.
• noun mathematics An additive inverse.
• adverb In an opposite position.
• preposition Facing, or across from.
• preposition In a complementary role to.

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

• adjective altogether different in nature or quality or significance
• adjective of leaves etc; growing in pairs on either side of a stem
• adjective characterized by opposite extremes; completely opposed
• noun something inverted in sequence or character or effect