The Collaborative International Dictionary of English v.0.48:

overcast \o`ver*cast"\, a.
   1. (Meteorology) Completely or almost completely covered over
      with clouds; -- of the sky.
      [PJC]

   2. (Sewing) Sewn by overcasting.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Overcast \O`ver*cast"\ ([=o]`v[~e]r*k[.a]st"), v. t.
   1. To cast or cover over; hence, to cloud; to darken.
      [1913 Webster]

            Those clouds that overcast your morn shall fly.
                                                  --Dryden.
      [1913 Webster]

   2. To compute or rate too high. --Bacon.
      [1913 Webster]

   3. (Sewing) To take long, loose stitches over (the raw edges
      of a seam) to prevent raveling.
      [1913 Webster]

   4. (Bookbinding) To fasten, as single sheets, by overcast
      stitching or by folding one edge over another.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

overcast
    adj 1: filled or abounding with clouds [syn: cloud-covered,
           clouded, overcast, sunless]
    n 1: the state of the sky when it is covered by clouds [syn:
         cloudiness, cloud cover, overcast]
    2: gloomy semidarkness caused by cloud cover [syn: cloudiness,
       overcast]
    3: a long whipstitch or overhand stitch overlying an edge to
       prevent raveling [syn: overcast, overcasting]
    4: a cast that falls beyond the intended spot
    v 1: make overcast or cloudy; "Fall weather often overcasts our
         beaches" [syn: overcast, cloud] [ant: brighten,
         clear, clear up, light up]
    2: sew over the edge of with long slanting wide stitches
    3: sew with an overcast stitch from one section to the next;
       "overcast books"