It's an expression of sarcasm when you don't believe something that somebody else has just said.
A nerdy guy tells you he has slept with at least 50 women during his university years.
"Yeah riiiight", - you reply in sarcastic voice, possibly with a bit of a smile.
5👍 1👎
Another example of sarcasm, intended to laugh mockingly at an insult your opponent has just said.
Him: "Boy, are you stupid or what!?"
Me: "Yeah okay buddy".
19👍 1👎