Ranting is the act of (often) pointless usage of the mouth, usually in a loud, negative and prolonged manner.

It is mostly heard in the form of a monologue and best practiced by annoyed politicians; the finest examples of this action can be found in the British House of Commons, (for my American friends who really want to see and hear this, tune into C-Span for Prime Minister's Question Time).

Other great examples of ranting can be heard from:

It can be great fun and a fantastic release to have a good ranting session, but beware your audience, it's a rare occasion when one finds a receptive set of ears for this bombastic, more often than not arrogant, form of communication