безмятежн|ость - ж. serenity, tranquillity, placidity;
~ый serene, placid, unruffled;
~ый покой unruffled serenity, undisturbed tranquillity;
~ый сон tranquil/untroubled slumber;
~ое детство unruffled childhood.
~ый serene, placid, unruffled;
~ый покой unruffled serenity, undisturbed tranquillity;
~ый сон tranquil/untroubled slumber;
~ое детство unruffled childhood.
Большой англо-русский и русско-английский словарь. 2001.