Vulpine means 'to do with foxes' or 'like a fox'. It works in two quite different ways. In its plain, scientific use it just labels something as belonging to foxes: vulpine behaviour, vulpine teeth, a vulpine species. Biologists, vets and nature writers use it this way, and it carries no feeling at all — it is simply the formal adjective for 'fox', the way 'canine' is for dogs and 'feline' is for cats. The second use is about people, and here it carries a strong flavour. Call a person's smile or manner vulpine and you mean they look clever in a way that makes you uneasy — sharp-eyed, quick, watching you, probably planning something. It suggests cunning rather than power. A vulpine face is usually a thin one with narrow eyes. This use lives almost entirely in novels and in careful, literary writing; it is not a word you will hear in conversation, and if you use it while chatting people will notice the shift in register. Whether it insults someone depends a little on the writer: sometimes it admires the cleverness, more often it warns you not to trust it. There is one thing worth knowing about the fox part. In English-speaking cultures the fox is above all sly and tricky — the animal that steals the chickens and outwits the farmer. It is a much closer match to 狐狸 than most animal words are across languages, though English does not carry the '狐狸精' idea of a seductive woman; for that, English says 'foxy', which is a completely separate and much more casual word.

狐狸的；似狐狸的（形容人時＝狡猾、精明而讓人不太放心的那種神情）