means A spin of the whole body on one foot, especially in ballet, executed in a single fluid turn.

from From French pirouette, 'a spinning top' or 'whirligig' — the word for a child's toy that twirls on its point became the word for a dancer who does the same. The French itself is of uncertain deeper origin, possibly built on piron, 'a peg' or 'pivot' (compare Italian piruolo, a spinning top), with the whirling ending of girouette, 'weathervane.' The image is honest: a body balanced on one tiny point, turning.