adjective
- pleasantly calm or peaceful; unruffled; tranquil; serenely quiet or undisturbed: placid waters.
adjective
- having a calm appearance or nature
adj.1620s, from French placide (15c.) and directly from Latin placidus “pleasing, peaceful, quiet, gentle, still, calm,” from placere “to please” (see please). Related: Placidly; placidness.