This is a phrase commonly used throughout the UK to indicate to a friend, colleague or even a total stranger that they have seriously annoyed a number of other people by word, action or attitude and that they can expect repercussions.
"Malcolm's just changed a whole load of databases that took months to set up, system support are fuming, he's really pissed them off!"
In baseball, when a batter hits the baseball with power. This type of hit normally results in a home run, however, it need not be a home run. It could be just a powerful hit!
Idiom meaning "Why are you in a bad mood?", implying discontent with the other person's attitude. As it is a rhetorical question, no response is expected. Often used in situations where the person being asked is angry as the result of an underlying cause and therefore snaps at people who have nothing to do with this cause.