リア充 is one of those Japanese words that uses bits of katakana (like ロリコン (lolicon) for example) and challenges the reader/listener to figure out what the hell it means. Luckily we have the internets. According to the survey:
In English, it means an enriched or full life. The ｢リア」part is the "rea" of "real" and the 「充」belongs to ｢充実」("fullness"). So the concept refers to someone who has his or her life together. Wikipedia corroborates! When we add the transformative, negative 非 kanji, we get the opposite of that. Japanarchist uses the term "loser." You could also go with "someone who sucks at life."
Looking at the survey, here are the top 10 traits of a loser:
1. マイナスな発言が多い (Says a lot of negative things)
2. 友達が少ない (Has few friends)
3. 恋人がいない (Has no partner/mate/lover)
4. 一日中誰とも会話しない日がしゅうちゅうある (Frequently goes the whole day without conversing with anyone)
5. 周りに興味がない (Isn't interested in anything around them)
6. オシャレに興味ない(Isn't interesting in style/fashion)
7. 恋愛に消極的 (Is half-hearted in romance)
8. 急に人に話しかけられると「えっ、あ、あの、あの」としどもどるになる (Becomes flustered and sputters when suddenly approached and spoken to by someone)
9. 非恋愛体質 (Uninterested in romance?)
10. 「自分はこんなもんじゃない」と常に思ってる (Always thinks "It's not my fault")[?]
I find all of these pretty understandable, but #6 kind of stands out to me as very "Japanese." 「オシャレ｣ is a little difficult to peg as precisely "style" or "fashion" but it is, I think, a fair generalization to say that Japanese people as a whole seem a lot more concerned with such things than many people of other nationalities. I can't say people don't care about style here in the U.S., for example, but I don't think I know many people who would place that in a top 10 list of "loser" characteristics. What do you think?