Amal-e-Katheer (excessive movement) refers to that act of a person praying which is not for the correction of the prayer, nor is it among the acts of the prayer, and it is done in such a manner that a sudden onlooker would think that this person is not in prayer. Such an act invalidates the prayer. Many people commit Amal-e-Katheer in prayer, due to which their prayer becomes invalid, but due to not knowing this definition of Amal-e-Katheer, they think that their prayer is valid. Therefore, one should stand in prayer with complete tranquility and calmness. (Tabyin al-Haqa'iq: 1/412) (Derived from: Darsi wa Talimi Aham Masail, pg: 112)