Tranquillity (also spelled tranquility) is the quality or state of being tranquil; meaning calmness, serenity, and worry-free.aps have been produced for the whole of England that show the tranquillity score of Ordnance Survey Grid derived 500mx500m squares. The tranquillity rating for these is based on 44 different factors that add to or detract from people’s feelings of tranquillity.