A comment to a post yesterday suggested that this was just the new name for Objection to Consideration. That's not really the case, although it may seem that way superficially.
Objection to Consideration is the parliamentary equivalent of a 16-ton weight dropping on your proposal. When a main motion (like a constitutional amendment) first comes up at the Preliminary Business Meeting, any member can immediately move to Object to the Consideration of the Question. Making this motion can interrupt another speaker who has been assigned the floor but who hasn't yet started speaking, and can take precedence over any other procedural motion that has been made but not yet put before the meeting by the Chair restating it. If a super-majority of the members vote against consideration, without debate, the main motion is dead for this year.
WSFS members have grown very fond of using this motion, even though it's really intended mainly to get rid of things that could potentially cause harm to the organization merely to discuss, such as motions of censure. Instead, it's been deployed against matters that were merely unpopular. In particular, people have been coming to WSFS meetings in good faith with proposals, not quite realizing the depth of dislike of a proposal among the people who attend the meeting regularly, and have had this nuclear bomb of a motion dropped on them before they even had a chance to make an opening statement. This leads to them coming away bitter and angry and inclined to bad-mouth "the SMOFS" for being completely unfair.
Some people (me among them) decided that while OTC has its use (the Chris Carrier motions of 1993 being a good example), it has been overused, primarily because WSFS hasn't had any good way of killing no-hope motions at the preliminary stage because the motion designed to do that, Postpone Indefinitely, was prohibited long ago by WSFS standing rules. (I'm not sure exactly why this was, other than the motion was being used to renew debate on issues. The rule passed long before I arrived in 1984.) So we crafted a couple of rule changes, one of which raised the necessary super-majority on OTC to 3/4, and one of which brought back Postpone Indefinitely as a permitted procedural motion, but in a limited form.
Postpone Indefinitely (PI) is the lowest-ranking of the procedural motions. It can only be made when nothing but the main motion is pending. If it passes (2/3 vote required by WSFS rule), the targeted main motion is dead for the duration of the current Worldcon. Because it's not a direct vote on the main motion, it can be made at the Preliminary Business Meeting. (By WSFS rule, it can only be made at the PBM.) This means that the PBM retains, as part of its agenda-setting authority, the ability to kill new business before it gets to the Main Meeting.
Unlike OTC, PI can be made even after amendments or debate on the main motion, as long as nothing is currently pending or nobody else has the floor. Also unlike OTC, PI is debatable. The motion to Postpone Indefinitely (by WSFS rule) has four minutes of debate time, evenly split between those who think we should consider the main motion, and those who do not want to even discuss it at the Main Meeting. This means that the proponents of a proposal will have at least two minutes to make the case for why we should consider their motion. They won't be squashed before they even got to make an opening argument. They may well still lose and see their proposal killed before the main debate, but they will have had at least one chance to make a case. In all but the most obnoxious proposals, I think that's fair.
If anyone moves a PI this year, it's my intention to first recognize the person who made the PI motion, who will have up to two minutes to say why we shouldn't consider the proposal. I will then recognize the lead sponsor present of the targeted proposal, who will have up to two minutes to say why we should consider it. I will then put the question in the form of "Shall [the targeted proposal] be considered? Those who think we should consider it, raise your hands... hands down. Those who think we should not consider it, raise your hands... hands down." (Putting it in this form means you vote in favor of or against the main motion, rather than having to invert your choices. It's also the way we voted on OTC, so regular attendees will recognize it.) If there is a two-thirds vote against consideration, the main motion is postponed indefinitely and is thus dead for the duration of the current Worldcon.
Note that Postpone Indefinitely in practice is likely to apply only to new constitutional amendments. It can't be applied to amendments awaiting ratification, and there are few circumstances in which it would make sense to apply it to resolutions, since the PBM can take a direct vote on them.
I hope that this reborn motion to Postpone Indefinitely puts a stop to the unseemly jack-in-the-box behavior of people leaping to their feet to shout "Objection to Consideration" to all new business, since there is a much more civilized way to clear the agenda without making newcomers to the Business Meeting feel that they're being deliberately shut up and told to Go Away.