v. t.
It would . . . deepen the bed of the Tiber. Addison. [ 1913 Webster ]
You must deepen your colors. Peacham. [ 1913 Webster ]
Deepens the murmur of the falling floods. Pope. [ 1913 Webster ]
v. i. To become deeper;
His blood-red tresses deepening in the sun. Byron. [ 1913 Webster ]