嘚瑟 [dè·se] (usually written 得瑟 in my limited observation) is apparently 东北方言. I've seen a couple dictionaries/explanations that say it means to "show off". I hear this word fairly frequently, but I haven't really grasped its full meaning yet. Is it just "show off" or is there a more subtle usage to it?
Doing a search in my WeChat 朋友圈 for 得瑟 gave me the following example. (Skip to the last line if the context is not important)
I believe the core of the meaning is overly expressive with gallantry or proudness.
Although the most common usages are when guys showing off in front of girls, it can be used in other contexts as well. For example if someone keeps talking proudly about some small deed to his friends, they may react with '你今天怎么这么嘚瑟？', which could be a neutral question, or '你嘚瑟个什么劲儿？', which is a slightly negative critique.
It used to be quite local in the northeast, but now gets used all over the places. It can mean showing off, attracting attention deliberately, and/or doing something without considering the impact. It's an informal but quite popular word now.