Sounding like a cough, or rough and harsh (as in 'hacky cough'); or relating to hack writers or poor-quality work.
From 'hack,' originally meaning to cough roughly, later extended to describe any cough-like sound. The adjective form emerged naturally for describing things with that rough quality.
A 'hacky sack' toy and a 'hacky cough' share the same root—both have that rough, chopped quality—showing how one word can split into separate meanings without losing its core feeling of jaggedness and incompleteness.
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