that ain't no lie

that ain't no lie

A very informal way of emphasizing that something that was just said is the truth. A: "We're gonna get in some serious trouble if we get caught." B: "That ain't no lie—so let's not get caught!" All this legal stuff at work has me really stressed out, and that ain't no lie.
See also: lie, no, that

That ain't no lie.

Rur. What was said is true. (The highly informal word ain't is built into the expression.) Tom: Sure is hot today. Jane: That ain't no lie. I'm plumb exhausted, and that ain't no lie.
See also: lie, no, that