The Collaborative International Dictionary of English v.0.48:

Noon \Noon\ (n[=o]n), a.
   No. See the Note under No. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Noon \Noon\ (n[=oo]n), n. [AS. n[=o]n, orig., the ninth hour,
   fr. L. nona (sc. hora) the ninth hour, then applied to the
   church services (called nones) at that hour, the time of
   which was afterwards changed to noon. See Nine, and cf.
   Nones, Nunchion.]
   1. The middle of the day; midday; the time when the sun is in
      the meridian; twelve o'clock in the daytime.
      [1913 Webster]

   2. Hence, the highest point; culmination.
      [1913 Webster]

            In the very noon of that brilliant life which was
            destined to be so soon, and so fatally,
            overshadowed.                         --Motley.
      [1913 Webster]

   High noon, the exact meridian; midday.

   Noon of night, midnight. [Poetic] --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Noon \Noon\, a.
   Belonging to midday; occurring at midday; meridional.
   --Young.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Noon \Noon\, v. i.
   To take rest and refreshment at noon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

noon
    n 1: the middle of the day [syn: noon, twelve noon, high
         noon, midday, noonday, noontide]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "noon":
   acme, apex, apogee, brow, cap, capstone, climax, cloud nine, crest,
   crown, culmen, culmination, edge, eight bells, extreme limit,
   extremity, heaven, heavens, height, high noon, highest pitch,
   highest point, limit, maximum, meridian, meridiem, midday,
   mountaintop, ne plus ultra, no place higher, noonday, nooning,
   noonish, noonlight, noonlit, noontide, noontime, not a soul, peak,
   pinnacle, pitch, point, pole, ridge, seventh heaven, sky, spire,
   summit, tip, tip-top, top, upmost, upper extremity, uppermost,
   utmost, vertex, very top, zenith