Definitions of grasp:

• noun:   a firm controlling influence

  Example: "A terrible power had her in its grasp"

• noun:   understanding of the nature or meaning or quality or magnitude of something

  Example: "He has a good grasp of accounting practices"

• noun:   the limit of capability
• noun:   the act of grasping
• verb:   hold firmly
• verb:   get the meaning of something