a sentry/security/patrol/guard dog

A (guardian) dog spirit; a attendant/familiar spirit: In Japanese mythology an inugami (lit. a "dog spirit") is a type of shikigami (式神), similar to a familiar spirit, resembling, and usually originating from, a dog, and most commonly carrying out vengeance or acting as guardians on behalf of their 'owner'.

(rare) A dog god

A term of affectionate for a dog or puppy. Compare English doggy.

(rare) female dog, she-dog, bitch

hearing dog (a dog trained to assist the deaf)

Alternative spelling of おおいぬ座 (“Canis Major”)

you should not interfere in a marital dispute

“even dogs wouldn't eat a marital dispute” → you should not interfere in a marital dispute

there is a danger of tragedy in any attempt / (idiomatic) good luck may come unexpectedly