Definition of "czar"

Note therfore that Czar in the Ruthens tounge signifieth a kynge, wheras in the language of the Slauons, Pollons, Bohemes, and other, the same woorde Czar, signifieth Cesar by whiche name Themperours haue byn commonly cauled.

1555, Peter Martyr d’Anghiera, translated by Richard Eden, The decades of the newe worlde or west India‎, London: William Powell, page 290

The federal mental health czar is calling for more money to expand services to help people suffering amid the social isolation imposed by the coronavirus pandemic […]

2020 May 8, Jayne O'Donnell, “'Deaths of despair': Coronavirus pandemic could push suicide, drug deaths as high as 150k, study says”, in USA Today‎, archived from the original on 9 May 2020