The Collaborative International Dictionary of English v.0.48:

Bond \Bond\ (b[o^]nd), n. [The same word as band. Cf. Band,
   Bend.]
   1. That which binds, ties, fastens, or confines, or by which
      anything is fastened or bound, as a cord, chain, etc.; a
      band; a ligament; a shackle or a manacle.
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            Gnawing with my teeth my bonds in sunder,
            I gained my freedom.                  --Shak.
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   2. pl. The state of being bound; imprisonment; captivity,
      restraint. "This man doeth nothing worthy of death or of
      bonds." --Acts xxvi.
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   3. A binding force or influence; a cause of union; a uniting
      tie; as, the bonds of fellowship.
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            A people with whom I have no tie but the common bond
            of mankind.                           --Burke.
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   4. Moral or political duty or obligation.
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            I love your majesty
            According to my bond, nor more nor less. --Shak.
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   5. (Law) A writing under seal, by which a person binds
      himself, his heirs, executors, and administrators, to pay
      a certain sum on or before a future day appointed. This is
      a single bond. But usually a condition is added, that,
      if the obligor shall do a certain act, appear at a certain
      place, conform to certain rules, faithfully perform
      certain duties, or pay a certain sum of money, on or
      before a time specified, the obligation shall be void;
      otherwise it shall remain in full force. If the condition
      is not performed, the bond becomes forfeited, and the
      obligor and his heirs are liable to the payment of the
      whole sum. --Bouvier. --Wharton.
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   6. A financial instrument (of the nature of the ordinary
      legal bond) made by a government or a corporation for
      purpose of borrowing money; a written promise to pay a
      specific sum of money on or before a specified day, given
      in return for a sum of money; as, a government, city, or
      railway bond.
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   7. The state of goods placed in a bonded warehouse till the
      duties are paid; as, merchandise in bond.
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   8. (Arch.) The union or tie of the several stones or bricks
      forming a wall. The bricks may be arranged for this
      purpose in several different ways, as in English bond or
      block bond (Fig. 1), where one course consists of bricks
      with their ends toward the face of the wall, called
      headers, and the next course of bricks with their lengths
      parallel to the face of the wall, called stretchers;
      Flemish bond (Fig.2), where each course consists of
      headers and stretchers alternately, so laid as always to
      break joints; Cross bond, which differs from the English
      by the change of the second stretcher line so that its
      joints come in the middle of the first, and the same
      position of stretchers comes back every fifth line;
      Combined cross and English bond, where the inner part of
      the wall is laid in the one method, the outer in the
      other.
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   9. (Chem.) A unit of chemical attraction between atoms; as,
      oxygen has two bonds of affinity. Also called chemical
      bond. It is often represented in graphic formul[ae] by a
      short line or dash. See Diagram of Benzene nucleus, and
      Valence. Several types of bond are distinguished by
      chemists, as double bond, triple bond, covalent
      bond, hydrogen bond.
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   10. (Elec.) A heavy copper wire or rod connecting adjacent
       rails of an electric railway track when used as a part of
       the electric circuit.
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   11. League; association; confederacy. [South Africa]
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             The Africander Bond, a league or association
             appealing to African, but practically to Boer,
             patriotism.                          --James Bryce.
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   Arbitration bond. See under Arbitration.

   Bond creditor (Law), a creditor whose debt is secured by a
      bond. --Blackstone.

   covalent bond, an attractive force between two atoms of a
      molecule generated by the merging of an electron orbital
      of each atom into a combined orbital in the molecule. Such
      bonds vary in strength, but in molecules of substances
      typically encountered in human experience (as, water or
      alcohol) they are sufficiently strong to persist and
      maintain the identity and integrity of the molecule over
      appreciable periods of time. Each such bond satisfies one
      unit of valence for each of the atoms thus bonded.
      Contrasted with hydrogen bond, which is weaker and does
      not satisfy the valence of either atom involved.

   double bond, triple bond, a covalent bond which
      involves the merging of orbitals of two (or three)
      electrons on each of the two connected atoms, thus
      satisfying two (or three) units of valence on each of the
      bonded atoms. When two carbon atoms are thus bonded, the
      bond (and the compound) are said to be unsaturated.

   Bond debt (Law), a debt contracted under the obligation of
      a bond. --Burrows.

   hydrogen bond, a non-covalent bond between hydrogen and
      another atom, usually oxygen or nitrogen. It does not
      involve the sharing of electrons between the bonded atoms,
      and therefore does not satisfy the valence of either atom.
      Hydrogen bonds are weak (ca. 5 kcal/mol) and may be
      frequently broken and reformed in solution at room
      temperature.

   Bond of a slate or lap of a slate, the distance between
      the top of one slate and the bottom or drip of the second
      slate above, i. e., the space which is covered with three
      thicknesses; also, the distance between the nail of the
      under slate and the lower edge of the upper slate.

   Bond timber, timber worked into a wall to tie or strengthen
      it longitudinally.
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   Syn: Chains; fetters; captivity; imprisonment.
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WordNet (r) 3.0 (2006):

covalent bond
    n 1: a chemical bond that involves sharing a pair of electrons
         between atoms in a molecule