[is that so] {informal}
1. Oh, indeed? That's interesting. — Used in simple acceptance or reply.
* /"The Republicans have pulled a trick at city hall." "Is that so?"/ 2. Surely not? — Used in disbelief or sarcasm.
* /"The moon is made of green cheese." "Is that so?"/* /"I'm going to take your girlfriend to the dance," said Bob. "Oh, is that so!" said Dick. "Try it and you'll be sorry."/