On December 10, 2010, at about 10:30 a.m., Sen. Bernie Sanders, I-Vt., took to the floor of the United States Senate to attack the deal struck between President Obama and Senate Republicans that extended the President Bush tax rates through the end of 2012. It was a Friday morning, and the Senate had no votes scheduled for the rest of the day, and no other senator wanted to speak.
Sanders then went on to rail against income inequality and Wall Street for almost 9 hours. Here are some of the headlines from media organizations the next day:
The Huffington Post: Bernie Sanders Filibuster: Senator Stalls Tax Cut Deal
The Los Angeles Times: Sen. Bernie Sanders ends filibuster
Talking Points Memo: Sanders Ends Daylong Filibuster Of Tax Cut Compromise
Of course, many of these same organizations are now insisting that whatever Sen. Ted Cruz, R-Texas, is doing to stop Obamacare funding right now on the Senate floor (he's been speaking for more than 17 hours), it is not a filibuster. Just look at Talking Points Memo, who has a post up titled, "Ted Cruz's Long Speech To Block Obamacare Funding Is No Filibuster." In the article, Sahil Kapur writes, "Sen. Ted Cruz took to the floor on Tuesday afternoon to speak until he is "no longer able to stand" in his quest to stop a bill that would fund Obamacare. But before you use the word "filibuster" — as Cruz's supporters are eager to do — the Texas Republican is procedurally limited by a vote scheduled to take place mid-day on Wednesday."
Nothing in Kapur's article explains why TPM considers the Sanders speech a filibuster, but not Cruz's.
As far as the "official" definition of "filibuster," there isn't one. The U.S. Senate defines "filibuster" as an "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."