na-adjective, noun
Colloquial term for someone, often a child or subordinate, being impudent or talking back. Carries a slightly old-fashioned, playful tone.
ちょこざいな口をきくな。
Don't talk back to me like that.
あの子はちょこざいで、すぐに生意気なことを言う。
That kid is cheeky and always says impertinent things.
生意気 is the standard, neutral term for impertinence, while ちょこざい is more colloquial and slightly dated.
The origin is uncertain. The kanji 猪口才 is ateji, and the word may derive from 猪口 (choko, a small sake cup) combined with 才 (sai, talent), but this is speculative.