Source : Webster's Revised Unabridged Dictionary (1913)

Decline \De*cline"\, v. i. [imp. & p. p. {Declined}; p. pr. &
   vb. n. {Declining}.] [OE. declinen to bend down, lower, sink,
   decline (a noun), F. d['e]cliner to decline, refuse, fr. L.
   declinare to turn aside, inflect (a part of speech), avoid;
   de- + clinare to incline; akin to E. lean. See {Lean}, v. i.]
   1. To bend, or lean downward; to take a downward direction;
      to bend over or hang down, as from weakness, weariness,
      despondency, etc.; to condescend. ``With declining head.''
      --Shak.

            He . . . would decline even to the lowest of his
            family.                               --Lady
                                                  Hutchinson.

            Disdaining to decline, Slowly he falls, amidst
            triumphant cries.                     --Byron.

            The ground at length became broken and declined
            rapidly.                              --Sir W.
                                                  Scott.

   2. To tend or draw towards a close, decay, or extinction; to
      tend to a less perfect state; to become diminished or
      impaired; to fail; to sink; to diminish; to lessen; as,
      the day declines; virtue declines; religion declines;
      business declines.

            That empire must decline Whose chief support and
            sinews are of coin.                   --Waller.

            And presume to know . . . Who thrives, and who
            declines.                             --Shak.

   3. To turn or bend aside; to deviate; to stray; to withdraw;
      as, a line that declines from straightness; conduct that
      declines from sound morals.

            Yet do I not decline from thy testimonies. --Ps.
                                                  cxix. 157.

   4. To turn away; to shun; to refuse; -- the opposite of
      accept or consent; as, he declined, upon principle.

Decline \De*cline"\, v. t.
   1. To bend downward; to bring down; to depress; to cause to
      bend, or fall.

            In melancholy deep, with head declined. --Thomson.

            And now fair Phoebus gan decline in haste His weary
            wagon to the western vale.            --Spenser.

   2. To cause to decrease or diminish. [Obs.] ``You have
      declined his means.'' --Beau. & Fl.

            He knoweth his error, but will not seek to decline
            it.                                   --Burton.

   3. To put or turn aside; to turn off or away from; to refuse
      to undertake or comply with; reject; to shun; to avoid;
      as, to decline an offer; to decline a contest; he declined
      any participation with them.

            Could I Decline this dreadful hour?   --Massinger.

   4. (Gram.) To inflect, or rehearse in order the changes of
      grammatical form of; as, to decline a noun or an
      adjective.

   Note: Now restricted to such words as have case inflections;
         but formerly it was applied both to declension and
         conjugation.

               After the first declining of a noun and a verb.
                                                  --Ascham.

   5. To run through from first to last; to repeat like a
      schoolboy declining a noun. [R.] --Shak.

Decline \De*cline"\, n. [F. d['e]clin. See {Decline}, v. i.]
   1. A falling off; a tendency to a worse state; diminution or
      decay; deterioration; also, the period when a thing is
      tending toward extinction or a less perfect state; as, the
      decline of life; the decline of strength; the decline of
      virtue and religion.

            Their fathers lived in the decline of literature.
                                                  --Swift.

   2. (Med.) That period of a disorder or paroxysm when the
      symptoms begin to abate in violence; as, the decline of a
      fever.

   3. A gradual sinking and wasting away of the physical
      faculties; any wasting disease, esp. pulmonary
      consumption; as, to die of a decline. --Dunglison.

   Syn: {Decline}, {Decay}, {Consumption}.

   Usage: Decline marks the first stage in a downward progress;
          decay indicates the second stage, and denotes a
          tendency to ultimate destruction; consumption marks a
          steady decay from an internal exhaustion of strength.
          The health may experience a decline from various
          causes at any period of life; it is naturally subject
          to decay with the advance of old age; consumption may
          take place at almost any period of life, from disease
          which wears out the constitution. In popular language
          decline is often used as synonymous with consumption.
          By a gradual decline, states and communities lose
          their strength and vigor; by progressive decay, they
          are stripped of their honor, stability, and greatness;
          by a consumption of their resources and vital energy,
          they are led rapidly on to a completion of their
          existence.

Source : WordNet®

decline
     n 1: change toward something smaller or lower [syn: {diminution}]
     2: a condition inferior to an earlier condition; a gradual
        falling off from a better state [syn: {declination}] [ant:
         {improvement}]
     3: a gradual decrease; as of stored charge or current [syn: {decay}]
     4: a downward slope or bend [syn: {descent}, {declivity}, {fall},
         {declination}, {declension}, {downslope}] [ant: {ascent}]
     v 1: grow worse; "Conditions in the slum worsened" [syn: {worsen}]
          [ant: {better}]
     2: refuse to accept; "He refused my offer of hospitality" [syn:
         {refuse}, {reject}, {pass up}, {turn down}] [ant: {accept}]
     3: show unwillingness towards; "he declined to join the group
        on a hike" [syn: {refuse}] [ant: {accept}]
     4: grow smaller; "Interest in the project waned" [syn: {go down},
         {wane}]
     5: go down; "The roof declines here"
     6: go down in value; "the stock market corrected"; "prices
        slumped" [syn: {slump}, {correct}]
     7: inflect for number, gender, case, etc., "in many languages,
        speakers decline nouns, pronouns, and adjectives"