Definitions of deepen:

• verb:   become deeper in tone

  Example: "Her voice deepened when she whispered the password"

• verb:   make deeper

  Example: "They deepened the lake so that bigger pleasure boats could use it"

• verb:   become more intense

  Example: "His dislike for raw fish only deepened in Japan"

• verb:   make more intense, stronger, or more marked

  Example: "This event only deepened my convictions"