slack up meaning
UK /slæk ʌp/ US /slæk ʌp/ 2 syllables
slack up (verb): make less active or fast.
Definition of slack up
How to pronounce slack up
slack up is pronounced /slæk ʌp/ in British English and /slæk ʌp/ in American English. It has 2 syllables.
More about slack up on Wikipedia.