(literally) between a dog and a wolf / (by extension, idiomatic) at dusk, at twilight; gloaming / (photography) golden hour (used in same technical sense for “good photographic light at twilight”)

(slang, of a man) junkyard dog

(simile) sick as a dog, sick as a parrot

(figuratively) imploring look, pathetic look, hangdog look

a disobedient animal or a person

barking dogs seldom bite, one's bark is worse than one's bite, all talk no bite

(very rare) an aggressive person will inevitably get themselves hurt

(of the weather) awful, dreadful

(simile) very suddenly and incongruously

female equivalent of chien (“bitch, female dog”) / a bitch (objectionable woman) / a whore; a prostitute