The Collaborative International Dictionary of English v.0.48:

Stability \Sta*bil"i*ty\ (st[.a]*b[i^]l"[i^]*t[y^]), n. [L.
   stabilitas; cf. F. stabilit['e]. See Stable, a.]
   1. The state or quality of being stable, or firm; steadiness;
      stableness; firmness; strength to stand without being
      moved or overthrown; as, the stability of a structure; the
      stability of a throne or a constitution.
      [1913 Webster]

   2. Steadiness or firmness of character; firmness of
      resolution or purpose; the quality opposite to
      fickleness, irresolution, or inconstancy; constancy;
      steadfastness; as, a man of little stability, or of
      unusual stability.
      [1913 Webster]

   3. Fixedness; -- as opposed to fluidity.
      [1913 Webster]

            Since fluidness and stability are contrary
            qualities.                            --Boyle.
      [1913 Webster]

   Syn: Steadiness; stableness; constancy; immovability;
        firmness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

stability
    n 1: the quality or attribute of being firm and steadfast [syn:
         stability, stableness] [ant: instability,
         unstableness]
    2: a stable order (especially of society) [ant: instability]
    3: the quality of being enduring and free from change or
       variation; "early mariners relied on the constancy of the
       trade winds" [syn: constancy, stability] [ant:
       changefulness, inconstancy]