1. (v. t.) To make deep or deeper; to increase the depth of; to sink lower; as, to deepen a well or a channel.

2. (v. t.) To make darker or more intense; to darken; as, the event deepened the prevailing gloom.

3. (v. t.) To make more poignant or affecting; to increase in degree; as, to deepen grief or sorrow.

4. (v. t.) To make more grave or low in tone; as, to deepen the tones of an organ.

5. (v. i.) To become deeper; as, the water deepens at every cast of the lead; the plot deepens.

accelerate agent provocateur aggravate amplify annoy augment beef up blow up broaden build up burrow complicate concentrate condense consolidate countersink depress deteriorate dig dig out dive double dredge drill embitter enhance enlarge exacerbate exaggerate exasperate excavate expand extend heat up heighten hop up hot up increase intensify irritate jazz up key up lower magnify make acute make complex make worse mine mount outspread outstretch provoke ramify redouble reinforce rise rouse scoop out sharpen sink soup up sour spread spread out step up strengthen triple tunnel whet widen worsen