boldface
Thick, dark print used to make words stand out.
Boldface is a style of printed or typed letters that are thicker and darker than normal text, making them stand out on the page. The word you're reading right here is in boldface. When you see text in boldface, it jumps out at you because the letters are heavier and more prominent than the surrounding words.
Writers and editors use boldface to draw your attention to important information. In a textbook, vocabulary words often appear in boldface so you can spot them easily when reviewing a chapter. In a recipe, the ingredients might be in boldface so you can quickly see what you need. Instructions for a test might put important warnings in boldface: Read all questions carefully before beginning.
The word can also be a verb: to boldface something means to make it bold. An editor might tell a designer to boldface all the chapter titles in a book.
You might also hear someone say a person told a bold-faced lie, meaning a lie told with complete confidence and no shame, right to someone's face.