The expression is "and that's saying something", not just "saying something". It means that the comparison I've just made is especially apt considering the degree of what I've compared to. Her dog barks more than mine, and that's saying something.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
enoonthat's saying somethingI've found what you mention in the MacMillan, but yours is much more understandable. Thank you very much.