To lessen; to dull; to make less intense (said of emotions and non-physical things).
To become damped or deadened.
To become damp or moist.
To make damp or moist; to make moderately wet.
To make less harsh
To make something soft or softer.
To palatalize.
To become or make (a consonant) more lenis, to lenite.
To become soft or softer
To undermine the morale of someone (often soften up).