What does "filibuster" mean, in the context of the Senate? Well, how about:
To filibuster is to insist that a bill or nomination needs 60 votes.
That's it. That's what it means to filibuster something, where "insist" means to notify the majority that the bill or nomination will need 60 votes, and to be willing to follow up on that (if necessary) by whatever parliamentary procedures are appropriate, whether it is speaking on the Senate floor, or voting against cloture, or any other maneuvers.
Now, you'll notice that the definition does not involve actually talking endlessly on the Senate floor. That kind of "live" filibuster can happen, but it is clearly a subset of all filibusters. Nor does this definition require the filibuster to actually defeat the bill or nomination. After all, we refer to famous filibusters from the past as filibusters whether or not they ultimately succeeded; for a more recent example, no one believes that the Republicans did not filibuster the health care reform bill. And it doesn't even require a cloture vote. We can imagine circumstances in which the losing side doesn't bother to contest a cloture vote, even though everyone understands that the "real' vote on a bill is the cloture vote. If Harry Reid knows he only has 55 votes, whether he chooses to schedule a cloture vote is really about posturing and public relations (it's rare for the leadership in either House to bring up a bill knowing it will lose, unless they want to put people on record). Whether the insists on the vote or not, the bill was killed by a filibuster. Similarly, if the minority attempts to find 41 votes to block but fails, they may choose to agree to a unanimous consent agreement establishing a time certain for a vote, even though with 41 they would have objected and forced a cloture vote. Again, the decision not to force a vote under those conditions is just posturing and public relations. It is a filibuster (in this case, an unsuccessful filibuster) whether or not the minority contests a cloture vote. The decision that matters -- the one that makes it a filibuster -- is the decision to try to find 41 votes to block the bill or nomination. Not 51. 41.
Now, there actually two other kinds of filibusters in the Senate:
1: To stall, or delay. We can talk about how forcing the clerk to read a bill delayed the final vote on the bill. In its mildest form, that sort of filibuster isn't as much a threat to the particular bill or nomination; it's just a way for a minority to slow things down. It blends into...
2. To stall or delay in order to kill a bill or nomination by making the cost in floor time too high. On the the Senate floor, virtually everything can be done very quickly -- as long as everyone agrees to act quickly. If not, things can move very, very slowly, and the majority has a finite amount of floor time available. Minorities (even minorities of one) can slow things down enough that the majority, if it is relatively indifferent, might just move on to something else. This kind of filibuster doesn't exactly defeat a bill; it raises the costs of passing the bill (or nomination), potentially at least higher than the majority is willing to pay.
Both of these could be called filibusters...but they're not what people mean, I think, when they use the word. I'm okay with that; I'd suggest we use "stall" or "delay" or some such word for the first two. Which brings us back to:
To filibuster is to insist that a bill or nomination needs 60 votes to pass. A filibuster is a requirement that a bill or nomination takes 60 votes to pass.
At this point, you may be saying: tell me something I don't know! Of course Republicans are going to insist on everything getting enough votes to obtain cloture. Well, yes -- but the vocabulary we're using doesn't fit that. Here's an excellent example from Michael O'Brien in The Hill last week:
Republicans have warned they could filibuster a nominee if Obama names someone to the court who leans to far to the left. While Democrats only need a majority vote to win confirmation, they need 60 votes to win procedural motions on the nomination.This makes no sense! First, we're told that Republicans "could" filibuster. But then we're reminded, without qualification, that Democrats "need" 60 vote on "procedural motions." But the procedural motion that needs 60 is cloture, which only needs to be invoked if Republicans are using a filibuster! To be clear: there is absolutely no need for a 60 vote supermajority in the Senate except in case of filibuster.
The larger point here is that Republicans no longer make any distinction between opposing something and filibustering it. Under Senate rules, that is their right. But it makes no sense under those conditions to talk about a "possible" filibuster or a "threat" of filibuster. Of course the Republicans are using a filibuster -- not might use, not could use -- they are using a filibuster against the Supreme Court nomination, just as they've used a filibuster against everything else the Democrats have opposed. Reporters should not write about filibuster threats; they should write about the chances of a filibuster actually derailing a bill, or the chances of marginal GOP Senators joining the filibuster. If Republicans claim they are only considering a filibuster, ask yourself -- and reporters should ask them -- if there's any chance they would allow the bill or nomination to pass by a 53-47 vote; that is, if there's any chance they would vote for cloture but against the bill or nomination.. If not (and on the Supreme Court pick, I think it's wildly implausible to imagine a 53-47 confirmation vote), then there's nothing conditional about the filibuster, and it's bad reporting to talk about it as if there was any uncertainty at all about its use. The Republicans are in fact insisting on 60 votes for passage or confirmation. That is a filibuster. Full stop, period, end of story.