red line /ˌɹɛd ˈlaɪn/ noun2 •The thick red line on the ice which divides the rink in half. •(figurative) A boundary or limit which should not be crossed.The administration’s ultimatum now seems like cheap talk, and it illustrates the risks of carelessly drawing red lines and issuing highly public threats that won’t be enforced. — 2013 formsred lines
