Texas Sen. Ted Cruz has been talking on the floor since 2:41 pm Tuesday. But, is what he is doing qualify as a filibuster or just a very long speech?

GREAT FALLS, VA - JULY 4: Bacardi, a Tennessee walking horse dressed as a unicorn, waits for the start of the Great Falls 4th of July Hometown Parade on Thursday, July 4, 2013, in Great Falls, VA. (Photo by Jahi Chikwendiu/The Washington Post)

Democrats have spent much of the time since Cruz started speaking noting that he's not technically filibustering because there is a cloture vote set to happen later today.

But, here's the dirty little secret of a filibuster -- there is no real definition of it. Here's how the U.S. Senate defines it: "Informal term for any attempt to block or delay Senate action on a bill or other matter by debating it at length, by offering numerous procedural motions, or by any other delaying or obstructive actions."

We put the question of what is a filibuster to Paul Kane, resident WaPo congressional genius, and he drew a comparison to the talk-a-thon put on by Vermont Sen. Bernie Sanders back in 2010 to protest the tax deal.  A cloture vote had already been scheduled when Sanders started talking -- and went on after he finished.

"What Sanders did then is what Cruz is doing now -- trying to convince his colleagues to vote against the cloture motion," PK wrote to us in the wee hours of Wednesday morning. "If by some modern miracle Cruz were to succeed and tomorrow afternoon 41 senators voted no, what would we say happened? We would say they filibustered the [congressional resolution]."

And here's more from PK:

Here’s how strange this situation is. When Majority Leader Harry Reid’s office touts the growth of filibusters in the modern Senate, his advisers count the number of times he has to file a motion to break a filibuster and when those votes are held to invoke cloture. (See this great chart that Wonkblog put together in July to see the growth in those motions and votes.) So, when the Senate votes this afternoon on a 60-vote hurdle to continue advancing the bill, Reid’s office will count that vote as an attempted filibuster. Yet Democrats are arguing that the marathon speeches leading up to that vote, themselves, do not amount to a filibuster.

In short: The filibuster is a unicorn. It doesn't really exist -- so debating whether or not what Cruz is doing counts technically as a filibuster is a pointless exercise.