A recluse lives alone, works alone, eats alone, and generally stays away from other people. Anti-social old hermits are recluses, as are a lot of students during exam time.
In the early 13th century, a recluse was a person who shut out the world to go meditate on religious issues. But nowadays recluses can think about whatever they want while they're sitting in solitude — they're simply people who shy away from social interaction and live secluded lives. Or think of the Brown Recluse spider, who likes to hide out in dark old boots or undisturbed corners of the basement.