deepen

Short definition from Wiktionary

Verb

1. 1
   To make deep or deeper
2. 2
   To make darker or more intense; to darken
3. 3
   To make more poignant or affecting; to increase in degree
4. 4
   To make lower in tone
5. 5
   To make more thorough or extensive.
6. 6
   To make more intimate.
7. 7
   To make more sound or heavy.
8. 8
   To become deeper
9. 9
   To become darker or more intense
10. 10
    To become lower in tone
11. 11
    To become more thorough or extensive.
12. 12
    To become more intimate.
13. 13
    To become more sound or heavy.