slacken

As a verb slacken

is to gradually decrease in intensity or tautness; to become slack.

As a noun letup is

a pause or period of slackening.

Slacken is a related term of unbend.

As verbs the difference between slacken and unbend

is that slacken is to gradually decrease in intensity or tautness; to become slack while unbend is to free from flexure; to make, or allow to become, straight; to loosen.

Slacken is a related term of slide.

In lang=en terms the difference between slacken and slide

is that slacken is to make slack, less taut, or less intense while slide is to pass along smoothly or unobservedly; to move gently onward without friction or hindrance.

As verbs the difference between slacken and slide

is that slacken is to gradually decrease in intensity or tautness; to become slack while slide is (ergative) to (cause to) move in continuous contact with a surface.

As a noun slide is

an item of play equipment that children can climb up and then slide down again.

Dull is a related term of slacken.

In lang=en terms the difference between dull and slacken

is that dull is to lose a sharp edge; to become dull while slacken is to make slack, less taut, or less intense.

As verbs the difference between dull and slacken

is that dull is to render dull; to remove or blunt an edge or something that was sharp while slacken is to gradually decrease in intensity or tautness; to become slack.

As an adjective dull

is lacking the ability to cut easily; not sharp.

In transitive terms the difference between slacken and sag

is that slacken is to make slack, less taut, or less intense while sag is to cause to bend or give way; to load.

As verbs the difference between slacken and sag

is that slacken is to gradually decrease in intensity or tautness; to become slack while sag is to sink, in the middle, by its weight or under applied pressure, below a horizontal line or plane.

As a noun sag is

the state of sinking or bending; sagging.

As an initialism SAG is

(on a letter), Saint Anthony Guard (or Guide).

As an acronym SAG is

screen Actors Guild.

As a verb slacken is

to gradually decrease in intensity or tautness; to become slack.

In lang=en terms the difference between release and slacken

is that release is to lease again; to grant a new lease of; to let back while slacken is to make slack, less taut, or less intense.

As verbs the difference between release and slacken

is that release is to let go (of); to cease to hold or contain or release can be to lease again; to grant a new lease of; to let back while slacken is to gradually decrease in intensity or tautness; to become slack.

As a noun release

is the event of setting (someone or something) free (eg hostages, slaves, prisoners, caged animals, hooked or stuck mechanisms).

As verbs the difference between slacken and debilitated

is that slacken is to gradually decrease in intensity or tautness; to become slack while debilitated is past tense of debilitate.

As an adjective debilitated is

weakened.

As verbs the difference between flinch and slacken

is that flinch is to make a sudden, involuntary movement in response to a (usually negative) stimulus while slacken is to gradually decrease in intensity or tautness; to become slack.

As a noun flinch

is a reflexive jerking away.