Not the literal meaning of sound
, that is to say, cool, very good etc.
It is like reverse sexual innuendo
It means that you want to sex up
the person you are speaking to, or that you find them ridiculously sexy.
It can also be used as a joke, to the people who don't know what it means, them thinking you mean it literally, as in you think they are cool.
It comes from the West of Ireland radio show iGo Home with Fergal D'Arcy on i102104.
He heard one of his flat mates say it during sex.