Home › Words › S › slacknessslackness/ˈslæknəs/slackness means the state of being slack; the quality of having slack.slackness is pronounced /ˈslæknəs/.EtymologyFrom Middle English slacnesse, slakenes, slaknesse; equivalent to slack + -ness. Compare Old English slæcnes.nounThe state of being slack; the quality of having slack.Vulgarity in West Indian culture.A subgenre of dancehall music with sexual lyrics.Definitions & examples from Wiktionary (CC BY-SA 3.0).