かわいくない The first "ka" does not belong to the word. — Tae Kim's Japanese Grammar flashcard

Not cute

i-adjectives can be conjugated. Replace the "i" with "kunai" to get the negative form. Remark: "かわいい/kawaii - cute" is spelled with two "i" in the end, the last one is replaced.

Just in case you're wondering how to do that for na-adjectives: Remember that they acted as noun, so just append "janai".