You might not see a nut as an appetizing meal but another person who is really hungry can see that nut as a full course meal and make use of it.
It means that you should appreciate every nut that hits your stomach.
Person 1: Look at this sandwich... gross! Would you eat it if i gave it to you?
Person 2: Well, I am really hungry.
Person 1: I can't believe it! I guess one man's nut is another man's meal.
When men get together at an unnamed christian university, remove a majority of their clothing and eat pbj on hawaiian bread so as to be comfortable enough to talk about anything on their mind.
Hey Ethan! Come on over, it's manmeal night. Don't forget your man-thong.