adj

• (informal) Impudent; impertinent; impertinently bold, often in a way that is regarded as endearing or amusing.
  "'Shut up,' said Harrison. 'You chaps always behave as if you were jawin' us when we come to jaw you.' / 'You're a lot too cheeky,' said Craye."
• (informal, of swimwear, underwear, etc.) Tending to expose the cheeks of the buttocks.
  "Barry said he introduced the cheeky bikini to the Coast three years ago: "I took a theatrical garment worn for as long as there have been strippers and showgirls — the G-string — and put it on the beach and gave it a name and we sold a heap.""
• (Australian Aboriginal) Poisonous (of animals such as snakes), dangerous, cunning, violent, potent.
  "A death adder is cheeky, a tree snake quiet. Wasps are only cheeky if you hold them in your hand."
• (informal, UK, Commonwealth) Indulged in.
  "Although sometimes I'd award myself a cheeky McDonald's hangover treat if I did well."