<p><strong>Noun</strong></p><ul><li>A very slender line.</li><li>The lower edge of the hair, especially along the upper forehead: a hairline that slowly receded.</li><li>Worsted fabric woven with very fine lines or stripes.</li><li>Printing: a very thin line on the face of a type.</li><li>A style of type consisting entirely of such lines.</li><li>A thin rule for printing fine lines.</li><li>Undesirable vertical lines between letters, caused by worn matrices.</li></ul><p><strong>Adjective</strong></p><ul><li>Narrow or fine as a hair: a hairline fracture.</li></ul>