deepen

UK: /ˈdiːpən/ US: /ˈdipən/ ,(dē′pən)

WordReference Random House Learner's Dictionary of American English © 2025

deep•en /ˈdipən/   v. 

1. to (cause to) become deep or deeper: [no obj]:
   Our troubles are deepening the more we get into debt.
   [ ~ + obj]:
   a silence that only deepened the mystery.

WordReference Random House Unabridged Dictionary of American English © 2025

deep•en  (dē′pən), v.t., v.i. 

1. to make or become deep or deeper:
   Larger ships will be able to navigate the river after the main channel is deepened. The shadows deepened toward late afternoon.
2. Meteorology to decrease in atmospheric pressure:
   a deepening cyclone.

• deep + -en¹ 1595–1605

deep′en•er, n. 
deep′en•ing•ly, adv. 

Collins Concise English Dictionary © HarperCollins Publishers::

deepen / ˈdiːp^ən/ verb

1. to make or become deep, deeper, or more intense

ˈdeepener noun