[1] : The Collaborative International Dictionary of English v.0.48

obligation \ob"liga"tion\, n. f. obligation. l. obligatio. see
   oblige.
   1. the act of obligating.
      1913 webster

   2. that which obligates or constrains; the binding power of a
      promise, contract, oath, or vow, or of law; that which
      constitutes legal or moral duty.
      1913 webster

            a tender conscience is a stronger obligation than a
            proson.                               --fuller.
      1913 webster

   3. any act by which a person becomes bound to do something to
      or for another, or to forbear something; external duties
      imposed by law, promise, or contract, by the relations of
      society, or by courtesy, kindness, etc.
      1913 webster

            every man has obligations which belong to his
            station. duties extend beyond obligation, and direct
            the affections, desires, and intentions, as well as
            the actions.                          --whewell.
      1913 webster

   4. the state of being obligated or bound; the state of being
      indebted for an act of favor or kindness; -- often used
      with under to indicate being in that state; as, to place
      others under obligations to one.
      1913 webster

   5. law a bond with a condition annexed, and a penalty for
      nonfulfillment. in a larger sense, it is an acknowledgment
      of a duty to pay a certain sum or do a certain things.
      1913 webster

   days of obligation. see under day.

   under obligation, under an obligation. in a state of
      obligation4.
      1913 webster +pjc
see also:
oblige days of obligation day under obligation under an obligation 

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