An idiom meaning something so disliked or bad that nobody (not even a dog) will accept or eat it — used to say it's universally avoided or despised.
あの映画は評判が悪くて、犬も食わない出来だった。
That movie had such a bad reputation that it was something no one wanted (not even a dog would eat it).
彼らのゴシップは信頼性がなく、犬も食わない話だ。
Their gossip has no credibility — it's the sort of story nobody would touch.
あの店のサービスは悪く、常連客でさえ犬も食わないと言っている。
That shop's service is so bad that even regular customers say it's something no one would accept.