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]