A grande reverence is the elaborate curtsy performed by a female dancer after a performance to acknowledge the applause of the audience. Students, both male and female dancers, can also perform a grande reverence at the end of class to show respect to their teacher (and, if present, piano accompanist).
The grande reverence exercise is usually given by the teacher in the form of an adagio that often contains port de bras in various ballet positions, often ending with a final curtsy or bow. When done as the last exercise of a class, a reverence serves as a sort of “finish” to the class and as a gesture of mutual appreciation between teacher and student.