What does 'nerdy' mean?

Recently, I realized noticed that many people use the word 'nerdy' when they are introduce themselves. What does's that exactly mean, exactly? It's Is it a positive word or a negative word?

最近看到很多人在介绍自己的时候，经常会说自己是个 nerdy ，nerdy是什么意思？ 褒义词还是贬义词？

*instead of "...use the word 'nerdy' when they introduce themselves" you could say "...describe themselves as nerdy" or "...use the word 'nerdy' to describe themselves"

all are OK

What does 'nerdy' mean?

Recently, I realized (I have realized is a bit better) that many people use the word 'nerdy' when they introduce themselves (if you use "are", write "when they are introducing themselves"). What does that exactly mean? Is it a positive word or a negative word (While I know what you mean, it sounds more natural to say: Does this word have a positive or negative connotation?

If this is an actual question as well: Nerdy more or less refers to someone who is a 宅男. In high school if someone calls you a nerd it is probably seen as a "bad thing" in the United States. However, it can be a neutral word as well just to identify yourself as a part of a group.