Supervote is a term used on Wikipedia, often in a deletion review or move review, in reference to a discussion closure ("a close") that reflects the preference of the closer, rather than according to the content of the discussion. It is usually used as an accusation that this is the case, carrying the implication that the closer should have entered the discussion as a participant instead of closing, and that the close should be overturned.

Deletion discussions are closed to reflect the consensus in the discussion.

It should be noted that consensus discussions (including XfDs and RfCs) are not really polls. For example, if an XfD discussion has more "keeps" than "deletes" but the "deletes" are grounded in policy and the "keeps" are of the WP:ILIKEIT variety (or conversely if the deletes say WP:ITSCRUFT and the "keeps" are grounded in policy), it's not a "supervote" to close in accordance with a significant minority opinion. (See also WP:Deletion guidelines for administrators § Rough consensus.)

However, an XfD discussion is not an "admin's suggestion box" either. Unless there are serious policy problems with the majority view, a consensus heavily skewed to one side should not be closed the other way. For example, if the majority view at an AfD is based on a position that would clearly violate verifiability or BLP concerns, the majority is wrong. Similarly, it doesn't matter whether the majority wants to keep a file in a FfD debate if it would violate the non-free content policy, which is prescriptively enforced as a legal matter. If a person feels that the opinions expressed in an XfD are contrary to policy but is not certain, then it is better to comment instead of close. The point raised can help inform the discussion, and this may help someone else to close appropriately.

There are several varieties of supervote, all of them problematic except the last one:

• Consensus-reversal supervote: A discussion has concluded for a particular action, based on solid policy reasoning, but a minority takes a different view that has less backing. It is supervoting to close in favor of the dissenters. If a neutral closer would not have produced such a close, the discussion should not close that way.
• Pile-on supervote: A discussion has an emotive majority in favor of an outcome, but it is clearly against policy. It is a supervote to close the discussion in favor of the majority as such, ignoring the policy faults of their arguments. If an impartial closer would have used admin discretion to close against the majority, that is the way the decision should be closed.
• Forced-compromise supervote: A discussion has drawn to a close, with or without a clear outcome. It is supervoting to close in favor of an undiscussed or unfavored compromise idea, which may satisfy no one. If a discussion did not come to a consensus, it should be closed as such. If it did, it should be closed with that consensus, not with an "I'm going to force everyone to get along" attempt to split the difference. Attempts to do so often produce impractical or nonsensical results. Closers may add a note about significant dissenting viewpoints, caveats, and suggestions for future resolution or improvement, without trying to include them as part of the consensus determination, and this is sufficient.
• Withdrawal supervote: The original proposer may feel like the winds of the discussion have blown one way or the other, and feel like they should withdraw their ideas to let another action run its course. But it is not acceptable for proposers to withdraw for the purpose of getting a non-status-quo result or if somebody still dissents to the status quo, as it denies the result of a basis in the consensus of other involved editors.
• Left-field supervote: A discussion has drawn to a close, with or without a clear outcome. It is a supervote to close in favor of a solution no one even mentioned, or which was mentioned only in passing but not supported. If one has a solution to propose, it should be included in the discussion as a comment. If it's too late, it can be suggested in a later discussion. The extant discussion must have a close that reflects its actual contents. (But see next item.)
• Non-prejudicial supervote: (Covered in detail below.) A discussion has drawn to a close, with or without a clear outcome. A closer makes an editorial, rather than administrative decision, and it moots the discussion. Alone among supervote types, this kind is often not problematic, because anyone who objects may revert it (or expect the closer to revert), with discussion continuing or being closed differently.

A "non-prejudicial supervote" is when an XfD is closed either against the consensus in the discussion or where there is no clear consensus, though the closer has left a closing rationale that the close is an "editorial decision" and states what the actual consensus is (if there is one). For example, redirect is an acceptable compromise when consensus is against a standalone article but split among merge, redirect, and delete. It might also apply if an administrator closes an AfD with no !votes as "delete" but offers to restore the article upon request. As an editorial decision, the standard rules of consensus-building and edit-warring apply to the result of such a close so no attempt should be made to "administratively" enforce the result.

1. If you believe that a closure reflects the closer's own opinion instead of consensus, civilly ask the closer to revert their closure and !vote by their preferences. As closing deletion discussions is an administrative action, closers, administrator or non-administrator, are subject to the administrators' accountability policy, and must explain all closes when questioned. Be careful not to skip this step, or treat it as a mere formality.
2. If the closer refuses to revert or adjust their closure and you find their explanation insufficient, nominate the closure for review (WP:Deletion review for XfDs, WP:Move review, or WP:Administrators' noticeboard for RfCs and other discussions), to have the close itself discussed by the community.
3. If an editor repeatedly fails to close based on consensus, or refuses to respond to questions regarding possible supervotes, despite multiple warnings and overturned closures, they may be banned from closing deletion discussions by the community (usually at WP:ANI or WP:AN), or even desysopped by the Arbitration Committee.

• Wikipedia:Administrators' reading list § Closing discussions
• Wikipedia:Consensus
• Wikipedia:Ignore all rules
• Wikipedia:Snowball clause