I . v. a.
1.
Make deeper, increase the depth of.
2.
Make darker, make more intense, darken, intensify.
3.
Reduce to a lower tone, make more grave, lower.
4.
Make more impressive or efficient, intensify, strengthen, increase, heighten, make more vivid.
II . v. n.
Grow deeper, become deeper, increase, heighten, become intenser or more decided.