Coarse, Crude, Inferior
noun, な adjective, の adjective
If it's coarse in a bad way it's still coarse but it's also crude or inferior. You don't want a fuzzy sweater to be coarse, do you? Or a carpet? If they are, they're this kind of coarse.
そあく
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
粗悪なガソリンは、車の寿命を早める。
Crude gasoline will shorten a car’s lifespan.