Someone who hasn't gotten hooked up romantically, sexually, or with a date, in any way, shape, or form, in a long time or not at all; especially someone who has a difficult time getting hooked up, either with anyone at all, or with someone that he or she is genuinely interested in being hooked up with.
There are several signs of datelessness, which are as follows:
1. Few, if any, are interested in going out with the person in question.
2. The person in question only wants to go out with people who are out of his or her league.
3. The person in question is so obsessed with going out with those who have no interest in him or her that he or she has neglected the rest of the dating pool.
4. The person in question doesn't have the guts to ask anyone out.
5. The person in question can't get over one or more bad endings to relationships for an extended period of time.
6. The person in question has severe difficulty in getting over one or more bad rejections.
7. For an extended period, the person in question thinks that getting hooked up is not worth it with anyone at all, at least at this point in time, or with anyone that the person can find at this point in time.
Finally, please note that at least some people can get along fine with being dateless, at least sometimes, especially when it primarily involves sign #7, but when datelessness leads to desperation, or the "blues", for an extended period of time, it can become an issue.
Daniel is not a pervert, closet or otherwise, he's just been dateless for too long.