'Slackly' definitions:

Definition of 'slackly'

(from WordNet)
adverb
In a relaxed manner; not rigid; "his hands lay loosely" [syn: loosely, slackly]

Definition of 'Slackly'

From: GCIDE
  • Slackly \Slack"ly\, adv. In a slack manner. --Trench. [1913 Webster]