it's highly offensive; arousing aversion or disgust. cowboy...

It can also mean a horrible taste or a revolting idea or thing. Kids mainly use this adjective to describe food they don't want to eat, eg Mummy I can't eat those vegetables, they taste yucky.

It is more commonly spelled "yucky". It means disgusting, nasty, or unpleasing

Steven is right. And It's not "highly offensive." It's a word used by children (said of food, like Jura said) or by young teenagers, to express being grossed out in a (softly) sexual sense: "Eww! Kissing boys, yucky!"