Unruffled, a.
Etymology: [Pref. un- not + ruffled.]
Not ruffled or agitated; smooth; calm; tranquil; quiet. Calm and unruffled as a summer's sea. Addison.
Shades of meaning
Fernald has no entry of its own for unruffled; he lists it under calm.
He lists it without comment; the entries above explain its neighbors.