square one noun
[noncount] : the beginning stage or starting point
▪ His idea didn't work, so he had to go back to square one. [=he had to start over] ▪ They lost everything and found themselves back at square one.
▪ His idea didn't work, so he had to go back to square one. [=he had to start over] ▪ They lost everything and found themselves back at square one.
