Acharya Prashant defines life not as mere physical movement or biological functions like breathing and eating, but as the capacity for understanding and consciousness. He explains that true aliveness is found when one is pulled toward realization and cannot bear to exist without knowing the truth. This understanding brings a sense of lightness and joy, whereas a lack of understanding acts as a heavy burden of suffering. He emphasizes that being alive is characterized by energy, freedom, and a constant movement toward new challenges, while lifelessness is a state of defiance against realization.