The Collaborative International Dictionary
Forslack
Forslack \For*slack"\, v. t. [Pref. for- + slack to neglect.]
To neglect by idleness; to delay or to waste by sloth. [Obs.]
--Spenser.
Wiktionary
forslack
vb. 1 (context intransitive rare English) To slack up; be or grow slack; pall. 2 (context transitive obsolete English) To be slack in; neglect by idleness; relax; render slack; delay; lose or spoil by slackness.