From The Lightning Thief:
He was seven feet tall, easy, his arms and legs like something from the cover of Muscle Man magazine—bulging biceps and triceps and a bunch of other ’ceps, all stuffed like baseballs under vein-webbed skin. He wore no clothes except underwear—I mean, bright white Fruit of the Looms—which would’ve looked funny, except that the top half of his body was so scary. Coarse brown hair started at about his belly button and got thicker as it reached his shoulders. His neck was a mass of muscle and fur leading up to his enormous head, which had a snout as long as my arm, snotty nostrils with a gleaming brass ring, cruel black eyes, and horns—enormous black-and-white horns with points you just couldn’t get from an electric sharpener.