Chuffed is a British dialect term (mainly in Northern England) and means very pleased; delighted; satisfied. It is often used with the intensifier 'dead' so someone who is dead chuffed is very very pleased. It appears to have been first used in this context around 1855. An alternative adjective 'chuff' was used to mean swollen with pride or elated.
In American English and in Southern England chuffed can mean entirely the opposite - disgruntled; dissatisfied; or annoyed. A chuff was a boorish, surly fellow. The first known written use of it in this context appears to pre-date the above by about 30 years.
To have different meanings for the same word according to where you are is quite normal but for them to be diametrically opposed is quite unusual. How confusing is that?
Interestingly, in an interview with the then British PM Tony Blair, William Safire of the New York Times suggested "Annoyed" and "put off" were the synonyms of chuffed and asked Mr Blair to pinpoint the localities to which the term was native. Tony Blair responded by warning "Be careful how you use it." Safire took this as a signal that, in addition to the opposite senses, there might be other meanings, and found there is 'a noun form equivalent to duff, from American slang'. I can only guess at what that means; duff in English has the simple and innocent meaning of a stiff flour pudding, steamed or boiled and containing plums, currants and the like.
