Originally Posted by addabox
cleave: to adhere closely; stick; cling
cleave: to cut off; sever
As best I know the only word in English that is its own antonym.
When I read your post, I remembered that just the other day I heard a word that was it's own opposite, but couldn't remember it.
Apparently there is a word for that entire class of words: contronym
And "sanction" (which is on the list) was the word that I couldn't remember. I think they were discussing it on NPR during the Libya thing.
(How was that for a meta-post?)