There are untranslatable words in ANY modern language, but Russian is something clearly out of scale. The word above is not very common and completely made up, but we use it very often, and huge thanks to my friends for the definition above.)) КУКУСИК can also be translated as ‘cutie’ or even ‘sexy’, but one cannot say ‘you’re such a КУКУСИК’ - it doesn’t fit in. One can own a КУКУСИК, like, “awww, my hero КУКУСИК!”, etc. There’s a bit of mocking here, as well, because technically it’s a word for something worth admiring and caring, which contains the suffix “-ик” - it is common for the words that describe something small/fluffy/kawaii/naive/puppy eyes mode on. Also, even being male in origin, the word can be applied to female species.