to gradually decrease in intensity or tautness; to become slack

listen to the pronunciation of to gradually decrease in intensity or tautness; to become slack
İngilizce - İngilizce
slacken

He seemed tired, and the Rat let him rest unquestioned, understanding something of what was in his thoughts; knowing, too, the value all animals attach at times to mere silent companionship, when the weary muscles slacken and the mind marks time.

to gradually decrease in intensity or tautness; to become slack