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.

Source: Webster's Revised Unabridged Dictionary (1913)