That's the stuff British spoken language
Said when you think something is great; said to praise someone for something they have done well.
A: Mom, I got the highest mark on the Maths test! B: That's the stuff, sweetie!
Yeah, that's the stuff. Nothing like going to the pool on such a sultry afternoon like this.
Used to describe someone or something that is very cool or good
Used to say that someone should cool down or calm down
Used to describe something that is very fine, pleasing or excellent
Cool, great.
To be the most oustanding, excellent, or extreme example of something
The origin of this expression is not clear.
Meaning absolutely certain or without a doubt
I am as sure as God made little green apples that Peter's the one for you, you two make a beautiful couple.