Source : Webster's Revised Unabridged Dictionary (1913)

Deepen \Deep"en\, v. t. [imp. & p. p. {Deepened}; p. pr. & vb.
   n. {Deepening}.]
   1. To make deep or deeper; to increase the depth of; to sink
      lower; as, to deepen a well or a channel.

            It would . . . deepen the bed of the Tiber.
                                                  --Addison.

   2. To make darker or more intense; to darken; as, the event
      deepened the prevailing gloom.

            You must deepen your colors.          --Peacham.

   3. To make more poignant or affecting; to increase in degree;
      as, to deepen grief or sorrow.

   4. To make more grave or low in tone; as, to deepen the tones
      of an organ.

            Deepens the murmur of the falling floods. --Pope.

Deepen \Deep"en\, v. i.
   To become deeper; as, the water deepens at every cast of the
   lead; the plot deepens.

         His blood-red tresses deepening in the sun. --Byron.

Source : WordNet®

deepen
     v 1: make more intense, stronger, or more marked; "The efforts
          were intensified", "Her rudeness intensified his dislike
          for her"; "Potsmokers claim it heightens their
          awareness"; "This event only deepened my convictions"
          [syn: {intensify}, {compound}, {heighten}]
     2: become more intense; "The debate intensified"; "His dislike
        for raw fish only deepened in Japan" [syn: {intensify}]
     3: make deeper; "They deepened the lake so that bigger pleasure
        boats could use it"
     4: become deeper in tone; "His voice began to change when he
        was 12 years old"; "Her voice deepened when she whispered
        the password" [syn: {change}]