Today's Word of the Day means...
A period of inertness or decreased activity: He'd pulled his weight long enough to get some slack/ a channel surfer trapped in his own den of slack (1851+)verb
: Witness the 40,000 or so Americans here now, a lot of them teaching English or just slacking, drinking 50-cent beers in the pubs, grooving to acid jazz at the Roxy
Since Unix files are stored compactly, except for the unavoidable wastage in the last block or fragment, it might be said that "Unix has no slack".
See ha ha only serious.