dampen

To make damp or moist; to make moderately wet.transitive

To become damp or moist.intransitive

To lessen; to dull; to make less intense (said of emotions and non-physical things).transitive

• We won't let the bad news dampen our spirits.
• He was dreadfully familiar with everything, and talked about some places we were longing to see in a way that considerably dampened our enthusiasm.

To suppress vibrations (mechanical) or oscillations (electrical) by converting energy to heat (or some other form of energy).proscribedtransitive

To become damped or deadened.intransitive