Soemone who doesn't get out very much, ususally due to illness, handicap, old age.

A prisoner or recluse confined to a safe and comfortable area such as the home. The shut in lacks the capacity to regulate a stable social life as long as he or she is so confined, and in addition to a lack of healthy, natural sunlight, will usually become pale, depressed, insane, or generally pitiful in contrast to an outgoing individual. Synonymous with tight ass, worthless, stiff, and EverQuest player.

Somebody who doesn't get out enough. See loser or loner.