Ask HN: What does "learning" a language mean?

Heavily inspired by sbov's comment [0] on this [1] HN thread about this [2] Ars Technica article discussing this [3] StackExchange question. (An aside -- there has to be something interesting to say about fragmented discussions and different value added by different communities!)

I don't want to make any suggestions as to what it means because I'd like to hear what you think.

[0] http://news.ycombinator.com/item?id=3664054 [1] http://news.ycombinator.com/item?id=3663727 [2] http://arstechnica.com/business/news/2012/03/ask-stack-should-i-learn-a-new-programming-language.ars [3] http://programmers.stackexchange.com/questions/136133/why-should-i-learn-a-new-programming-language