Back to the Drawing Board means: Time to start all over again.
Example of use: “It looks like my plans to kill the weeds in the garden failed. Back to the drawing board.”
The origin of the idiom “back to the drawing board” is art. The saying is attributed to an American artist named Peter Arno, who published his cartoons in the New Yorker. In a comic strip from 1941, we see a man in a fancy suit, carrying a bunch of rolled up papers assumed to be mechanical drawings of an aircraft, walking away from a crashed plane. In the bubble above his head, we read “Well, back to the drawing board.”