The Collaborative International Dictionary of English v.0.48:

Moan \Moan\, v. t.
   1. To bewail audibly; to lament.
      [1913 Webster]

            Ye floods, ye woods, ye echoes, moan
            My dear Columbo, dead and gone.       --Prior.
      [1913 Webster]

   2. To afflict; to distress. [Obs.]
      [1913 Webster]

            Which infinitely moans me.            --Beau. & Fl.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Moan \Moan\ (m[=o]n), v. i. [imp. & p. p. Moaned (m[=o]nd); p.
   pr. & vb. n. Moaning.] [AS. m[=ae]nan to moan, also, to
   mean; but in the latter sense perh. a different word. Cf.
   Mean to intend.]
   1. To make a low prolonged sound of grief or pain, whether
      articulate or not; to groan softly and continuously.
      [1913 Webster]

            Unpitied and unheard, where misery moans. --Thomson.
      [1913 Webster]

            Let there bechance him pitiful mischances,
            To make him moan.                     --Shak.
      [1913 Webster]

   2. To emit a sound like moan; -- said of things inanimate;
      as, the wind moans.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Moan \Moan\, n. [OE. mone. See Moan, v. i.]
   1. A low prolonged sound, articulate or not, indicative of
      pain or of grief; a low groan.
      [1913 Webster]

            Sullen moans, hollow groans.          --Pope.
      [1913 Webster]

   2. A low mournful or murmuring sound; -- of things.
      [1913 Webster]

            Rippling waters made a pleasant moan. --Byron.
      [1913 Webster]

WordNet (r) 3.0 (2006):

moan
    n 1: an utterance expressing pain or disapproval [syn: groan,
         moan]
    v 1: indicate pain, discomfort, or displeasure; "The students
         groaned when the professor got out the exam booklets"; "The
         ancient door soughed when opened" [syn: groan, moan]