Yes, both are right but we'd rather use "sucks" for a situation. Ex: C'est relou : It sucks! For a person, "annoying" is a better translation. Ex: Il est ennuyant - Il est chiant - Il est relou : He's annoying

And by the way, this is a type of French slang called "verlan", which means "à l'envers". Words are back to front. For example, meuf = femme, ouf = fou, chelou = louche, etc.

prefect. thank you guys!

Relou = lourd . Dans ce cas "lourd" doesn't mean" heavy" but "annoying or boring" In fact it's a way of speaking (mainly by young people) where you change the order of syllables in a word. I suppose it's a way of trying to speak differently so other people don't understand what you're talking about

I think both dictionary and google are right :D