chara has several meanings: 1) a lie or joke "chara wo iu", 2) even, zero "kari / hanasi wo chara ni suru". However, chara chara is rather different. Of the various meanings, frivolous and talkative are most relevant.
It is hard to miss out on the chara-phenomenon for those that live in Japan. Especially in 2011, Fujimori Shingo (藤森慎吾) made it into a very popular concept. Rather than chara, it is chara chara "frivolous" and "talkative" which are most defining. It is something that you know when seen, but difficult to define. So I referred to the Wikipedia article on it. It gives several defining characteristics, which seem appropriate:
- salon-tanned skin
- brown or blonde-tanned hair
- always hitting on girls (nanpa)
- always going to random dinner dates (gōkon)
- wears various accessories
- from a girls perspective, charao are: easy to talk with, fun, easy to be with; however, likely to cheat
Men who are like this are charai. Look up 藤森慎吾, who is the representative example of this. In 2011, he also made popular the phrase "kimi mo kawawiiii ne", where kawawii is a contraction of kawaii.