From Longman Dictionary of Contemporary Englishdotted lineˌdotted ˈline noun [countable] TCNa series of printed or drawn dots that form a line → sign on the dotted line at sign2(4)
Examples from the Corpus
dotted line• It's better to forward them inline, that is, beneath a dotted line.• In b the slope of each dotted line is less than unity - in each case denoting negative allometry.• Cut along the dotted lines.• You may want another approach to get people to sign on the dotted line.• The lucky 10,000 have signed on the dotted line.• But how many of these companies forget about you once you've signed on the dotted line.• The dotted line in each diagram separates the superior courts from the inferior courts.From Longman Business Dictionarydotted lineˌdotted ˈline noun sign on the dotted lineLAW to agree officially to something by writing your name on an official or legal documentDemand that the repairs are done before you sign on the dotted line. 