interline /ˌɪntə(ɹ)ˈlaɪn/verb 3/ˈɪntə(ɹ)ˌlaɪn/ adjective 2forms 3 verb3 •To write or insert between lines already written or printed, as for addition or correction. •To imprint or mark with lines.For each contracted frown, / A crooked wrinkle interlines my brow: / Spend but one hour in frowns, and I shall look / Like to a beldam of one hundred years. — 1600 •To arrange in alternate lines. interline /ˈɪntə(ɹ)ˌlaɪn/ adjective2 •Between lines.Interline twitter occurs on interlaced displays at half the field-rate. — 1986 •Between (or with) two airlines.American Airlines and British Airways have an interline agreement to handle each other's baggage and to accept each other's tickets.I had an interline connection from Delta to AA in Dallas/Ft. Worth. formsinterlined · interlining · interlines