Synonyms for Deepen:

n.

absorb, expand, learn, master, acquire, retrain, extend, keep up, pick up, acquaint yourself with something, train, develop. echo, hollow, ring, dig out, reverberate, dig, swell, go off, deafen. complicate, defy, baffle, confound, redouble, aggravate, obscure, be (as) clear as mud, confuse, be beyond someone, mystify. channel, course, dash, catch, crest, burst, cast up, come in, break. grip, pulse, surge, engulf, run, come over, sweep over, grow, color. deepen (noun)
compound, intensify, change, heighten.

v.

change (verb)
change, intensify.
deepen (verb)
sink.
intensify (verb)
escalate, increase, emphasize, exaggerate, sharpen, accentuate, magnify, stress, heighten, underline, intensify.
make depth greater (verb)
expand, hollow, extend, dig out, dig.
make more intense (verb)
develop, redouble, grow, intensify, increase, magnify, aggravate, heighten.

Other synonyms:

confuse, descend into, deafen, mystify, develop, cast up, baffle, deteriorate. brighten, echo, defy, reverberate, bleach, complicate. confound, swell, bleed, mellow. crest, fade. channel, burst, dash. come in, gray. course. go down. catch. break. run. darken
blacken.

Usage examples for deepen

  1. The reply was: " As the light fades and the shadows deepen all the petty and exacting details vanish; everything trivial disappears, and I see things as they are, in great, strong masses; the buttons are lost, but the garment remains; the garment is lost, but the sitter remains; the sitter is lost, but the shadow remains; the shadow is lost, but the picture remains. – Whistler Stories by Don C. Seitz
  2. She looked up, staring into his face and he saw an incredulous surmise deepen into certainty. – Mary Wollaston by Henry Kitchell Webster
  3. The poor Giacomo will not listen to me, he grows weak and childish, and he loved the master too well- better," and here her voice would deepen into reproachful solemnity, " yes, better actually than St. Joseph himself! – Vendetta A Story of One Forgotten by Marie Corelli