The best replacement for flack is flak.

The best alternatives to flack are rated as following:
★★★★★  flak
★★  hack
★  slack

Your alternative for flack is not listed? Suggest!
Speaking about flack, one probably shouldn't forget about donny hathaway.

Other search terms related to flack and their ratings are:
★★★★★ donny hathaway
★ olly murs
★ james arthur
You have in mind a companion for flack and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of flack in all years. Click on graph for more.
flack
flak
hack