|Origin:||placidus, from placere; PLEASE2|
a placid person does not often get angry or upset and does not usually mind doing what other people want them to:
a large, placid baby
She sat still, placid and waiting.
calm and peaceful:
The lake was placid and still under the moonlight.
Dobbs stood at the entrance, placidly smoking his pipe.
—placidity noun [uncountable]