When you've gone all day without eating anything, you'll probably devour your dinner, especially if it's your very favorite homemade lasagna. Devour means to eat greedily and hungrily.
The meaning of devour has grown to include the consumption of things other than food. If you sit down to start a book and look up ten hours later having turned the last page, you have devoured that book. If your after school job devours all your free time, chances are your grades are going to drop. The Latin root, devorare, means "to swallow down."