The Collaborative International Dictionary of English v.0.48:

Equable \E"qua*ble\ (?; 277), a. [L. aequabilis, fr. aequare to
   make level or equal, fr. aequus even, equal. See Equal.]
   1. Equal and uniform; continuing the same at different times;
      -- said of motion, and the like; uniform in surface;
      smooth; as, an equable plain or globe.
      [1913 Webster]

   2. Uniform in action or intensity; not variable or changing;
      -- said of the feelings or temper.
      [1913 Webster]

WordNet (r) 3.0 (2006):

equable
    adj 1: not varying; "an equable climate"
    2: not easily irritated; "an equable temper"; "not everyone
       shared his placid temperament"; "remained placid despite the
       repeated delays" [syn: equable, even-tempered, good-
       tempered, placid]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "equable":
   accordant, alike, automatic, balanced, calm, collected, composed,
   consistent, consonant, constant, continuous, cool, correspondent,
   dispassionate, easygoing, equal, equivalent, even, even-tempered,
   flat, homogeneous, immutable, imperturbable, invariable, level,
   level-headed, levelheaded, measured, mechanical, methodic,
   methodical, monolithic, of a piece, ordered, orderly, peaceful,
   persistent, placid, regular, reposeful, robotlike, same, serene,
   smooth, stabile, stable, steadfast, steady, systematic, tranquil,
   unbroken, unchangeable, unchanged, unchanging, undeviating,
   undifferentiated, undiversified, unflappable, uniform, unruffled,
   unvaried, unvarying