I skimmed the article and missed the definition as well. Now that's certainly my fault, and I knew that if my curiosity were peaked I'd go back and read the article more carefully.

But I'd also like to say that, IMHO, the fonts, spacing, various headings, images and codeblocks with dark background are all mixed up on that page, and the *bold* text does not stand out at all. Every other sentence or piece of information on that page is highlighted in its own way.