What do you mean by saying so?

问题描述:

What do you mean by saying so?
What do you mean by/of saying so?应该用哪个介词,为什么?

by
比如:
What do you mean by "Black Death"?
你说的“黑死病”是什么意思?
What do you mean by quantity discount?
您所说的数量折扣指的是什么?