The Collaborative International Dictionary of English v.0.48:

Pentameter \Pen*tam"e*ter\, n. [L., fr. Gr. ?; ? (see Penta-)
   + ? measure.] (Gr. & L.Pros.)
   A verse of five feet.
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   Note: The dactylic pentameter consists of two parts separated
         by a di[ae]resis. Each part consists of two dactyls and
         a long syllable. The spondee may take the place of the
         dactyl in the first part, but not in the second. The
         elegiac distich consists of the hexameter followed by
         the pentameter. --Harkness.
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The Collaborative International Dictionary of English v.0.48:

Pentameter \Pen*tam"e*ter\, a.
   Having five metrical feet.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Verse \Verse\ (v[~e]rs), n. [OE. vers, AS. fers, L. versus a
   line in writing, and, in poetry, a verse, from vertere,
   versum, to turn, to turn round; akin to E. worth to become:
   cf. F. vers. See Worth to become, and cf. Advertise,
   Averse, Controversy, Convert, Divers, Invert,
   Obverse, Prose, Suzerain, Vortex.]
   1. A line consisting of a certain number of metrical feet
      (see Foot, n., 9) disposed according to metrical rules.
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   Note: Verses are of various kinds, as hexameter,
         pentameter, tetrameter, etc., according to the
         number of feet in each. A verse of twelve syllables is
         called an Alexandrine. Two or more verses form a
         stanza or strophe.
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   2. Metrical arrangement and language; that which is composed
      in metrical form; versification; poetry.
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            Such prompt eloquence
            Flowed from their lips in prose or numerous verse.
                                                  --Milton.
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            Virtue was taught in verse.           --Prior.
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            Verse embalms virtue.                 --Donne.
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   3. A short division of any composition. Specifically:
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      (a) A stanza; a stave; as, a hymn of four verses.
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   Note: Although this use of verse is common, it is
         objectionable, because not always distinguishable from
         the stricter use in the sense of a line.
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      (b) (Script.) One of the short divisions of the chapters
          in the Old and New Testaments.
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   Note: The author of the division of the Old Testament into
         verses is not ascertained. The New Testament was
         divided into verses by Robert Stephens [or Estienne], a
         French printer. This arrangement appeared for the first
         time in an edition printed at Geneva, in 1551.
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      (c) (Mus.) A portion of an anthem to be performed by a
          single voice to each part.
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   4. A piece of poetry. "This verse be thine." --Pope.
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   Blank verse, poetry in which the lines do not end in
      rhymes.

   Heroic verse. See under Heroic.
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WordNet (r) 3.0 (2006):

pentameter
    n 1: a verse line having five metrical feet