[syn: equable, even-tempered, good-tempered, placid]
The Collaborative International Dictionary of English v.0.48:
Placid \Plac"id\, a. [L. placidus, originally, pleasing, mild,
   from placere to please: cf. F. placide. See Please.]
   Pleased; contented; unruffied; undisturbed; serene; peaceful;
   tranquil; quiet; gentle. "That placid aspect and meek
   regard." --Milton. "Sleeping . . . the placid sleep of
   infancy." --Macaulay.
   [1913 Webster]
WordNet (r) 3.0 (2006):
placid
    adj 1: (of a body of water) free from disturbance by heavy
           waves; "a ribbon of sand between the angry sea and the
           placid bay"; "the quiet waters of a lagoon"; "a lake of
           tranquil blue water reflecting a tranquil blue sky"; "a
           smooth channel crossing"; "scarcely a ripple on the still
           water"; "unruffled water" [syn: placid, quiet,
           still, tranquil, smooth, unruffled]
    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:
75 Moby Thesaurus words for "placid":
   affliction, at rest, bane, besetment, bother, botheration, calm,
   cloistered, collected, composed, cool, coolheaded, curse, detached,
   disease, dwindling, easy, easygoing, ebbing, epidemic,
   even-tenored, exasperation, halcyon, hushed, impassive,
   inexcitable, infestation, invasion, irenic, irritant, isolated,
   moldering, nuisance, outbreak, pacific, peaceable, peaceful, pes,
   pest, pestilence, philosophical, plague, poised, quiescent, quiet,
   rash, ravage, reposeful, reposing, restful, resting, scourge,
   secluded, self-possessed, sequestered, sequestrated, serene,
   sheltered, smooth, still, still as death, stillish, stilly, stoic,
   stolid, subsiding, tranquil, unagitated, undisturbed, unmoved,
   unperturbed, unruffled, unstirring, untroubled, waning