Clever in a sneaky way. A wily person gets what they want by planning, by tricking others, or by seeing a trap before anyone else does — not by being strong and not by being honest. Say it as /ˈwaɪ-li/, two syllables, and note that it rhymes with 'smiley', not with 'silly'. The word carries a mix of feelings that is hard to pin down. Most of the time there is a smile inside it: a wily old fox, a wily negotiator, a wily grandmother who always knows when you are lying. You are half-complaining and half-admiring. It is not the flat insult that 'dishonest' or 'sly' would be — 'sly' feels cold and unpleasant, 'wily' feels like the person is playing a game and playing it well. That is why it attaches so easily to animals in stories, to old people who have seen everything, and to politicians and lawyers, where people accept that tricks are part of the job. Though actually, if you use it about someone who cheated you out of real money, the smile disappears and it just means 'he fooled me'. So the same word can be light or heavy depending on who was hurt. It is a slightly bookish, storybook word — you meet it in novels and news writing much more than in everyday speech, where people would just say 'he's clever' or 'he's sneaky'. It only works before a noun or after 'be'; there is no verb and no common adverb (people avoid 'wilily' because it is hard to say). The noun 'wiliness' exists but is rare.