Placid (?), 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]