rotation (rotations plural )
1 n-var Rotation is circular movement. A rotation is the movement of something through one complete circle.
...the daily rotation of the earth upon its axis.
2 n-uncount The rotation of a group of things or people is the fact of them taking turns to do a particular job or serve a particular purpose. If people do something in rotation, they take turns to do it.
Once a month we met for the whole day, and in rotation each one led the group.