[boas]

Exactly. Dictionaries don't always reflect current usage. Take a look at how the Oxford English Dictionary defines "sarcastic": "a sharp, bitter, or cutting expression or remark." By that definition, "you're stupid!" is sarcastic.

[Jach]

I like to emphasize "Dictionary editors are historians of usage, not legislators of language." ( http://lesswrong.com/lw/od/37_ways_that_words_can_be_wrong/ )