In fact, the term 'man bites dog' exists longer than the movie :-)
It's used by belgian (and maybe some other countries) teachers to explain the importance of the position of various parts in a sentence. If you switch 'man' and 'dog', the sentence gets a whole new meaning, the words have another grammatical role.
eg. In English, French or Dutch this sequence of words is extremely important but in languages like German, Greek or Latin (where more cases exist) this is less important because if the function of a word changes, the article and the noun's ending changes. That way you can derive the function in the sentence.
Interestingly JerboaKolinowski mentioned a whole other meaning :-)
'Man bites dog' is a story that's interesting enough to print in a newspaper, as opposed to 'dog bites man', which is normal, dull and hence not newsworthy.