stiff

stiff as a board (of a person or part of the body) extremely stiff. informal

a stiff upper lip a quality of uncomplaining stoicism.

☞ This is a characteristic particularly associated with the British but the phrase is apparently North American in origin, dating back to the mid 19th century. It is used, for example, in Harriet Beecher Stowe's novel Uncle Tom's Cabin, published in 1852.

2014New York Times The ballet is a salute to Britain, and Balanchine catches several layers of the British persona: reverence and irreverence, the stiff upper lip and the twinkling eye.