Q: My smartest, best-dressed college football friends keep talking about “Blood Week.” What does that term mean?

A: A Blood Week — as defined by the Shutdown Fullcast, originators and trusted keepers of the term — is any week when the given season’s hierarchy is flipped upside down, when the sport’s propensity for chaos is turned to maximum levels.

Blood Week is not literally about blood, but think of the top 25 as an organism. Blood Week is the surprise week each year when several of its limbs get chopped off and an organ or two liquefies internally.

Everyone likes upsets, and no sport produces regular-season upsets that instantly matter more than college football’s. CFB fans love nothing more than they love these mass-uprising weekends. So here’s a name for that moment.

Q: Do you have a less vague answer than that?

A: There aren’t precise requirements, because a Blood Week is a thing you know by feel.

But! To avoid you having to tweet us every time Virginia Tech loses as a #23 team, asking if that counts, let’s lay out some theoretical conditions for a week to enter eligibility. You will probably need:

At least five ranked teams suffering upset losses (we’ll come back to that),

with at least two being top-10 teams at the time.

That doesn’t guarantee you’re looking at a Blood Week, because maybe some extenuating circumstance meant everyone kinda expected a top-10 team to lose to an unranked team, but it’s a good starting point.

Q: Is this the only way something can be a Blood Week?

A: Probably not! If, say, every team from #11 down to #25 lost to an unranked team in a single week, yeah, that would probably qualify. If the top two teams lost to FCS teams but nobody else in the top 25 got upset, well, that still might be the greatest Blood Week of all time.

Q: When does one realize a weekend has become a Blood Week?

Once multiple top-10 teams have lost, you might be getting close, especially if a big upset happens before Saturday even begins.

They’re hard to see coming in advance, but they typically strike in the latter half of the season.

In fact, after going through more than 80 years of rankings history, it’s clear the most common Blood Week is two weeks before Thanksgiving. Total mayhem has struck in that weekend about a dozen times, including 2016 (unranked wins over #2 Michigan, #3 Clemson, #4 Washington, #8 Auburn, #10 Texas A&M, #15 North Carolina, and #18 Virginia Tech).

Q: What were you going to say about upset losses?

A: This is another element that’s more about feel than numbers. Is the #13 team beating the #10 team an upset? Vegas might have the #13 team as a slight underdog or even a favorite, so it’s likely not earth-shattering. Blood Week demands more than that.

Q: That many upsets seems like a tall order. Do those happen all that often?

A: They’ve happened at least once for almost every season since the AP Poll began in 1936. (The week before Thanksgiving that year, significantly lower-ranked teams beat #1 Northwestern and #7 Marquette while unranked teams beat #3 Fordham, #14 Texas A&M, #17 Holy Cross, and #20 Temple.)

There are even Blood Weeks in seasons that seem, to the untrained eye, to be totally chalky. In 2018, the latest in a long line of two-sport dynasties ruling college football, we still had two chaos weekend-like periods:

In Week 7, we saw #2 Georgia, #6 West Virginia, #7 Washington, #8 Penn State, #16 Miami, #19 Colorado, and #21 Auburn lose to big underdogs and/or significantly lower-ranked teams.

And in bowl season, nine higher-ranked teams lost, including one of the most stunning point-spread results in title game history.

Q: Wait, you can have more than one Blood Week in a season?

A: Sure can! 1990, 2003, and 2007 had something like five Blood Weeks each.

Q: But not every season has one, right?

The last season without a Blood Week was arguably 2005, when a few teams really towered over the rest. The 1970s were light on Blood Weeks — anyone who thinks the top level of college football is stratified now should go back and look at that decade.

Q: What was that about Blood Week in bowl season? That’s a month, not a week.

A: Agree on the latter point.

The modern bowl structure usually means top-10 teams only play each other, and if a top-25 team draws an unranked team, it’s still at least a decent team. That isn’t all that conducive to Blood Week-style upsets.

So for the postseason, let’s loosen the rules to acknowledge things like “that time the SEC West was the toughest place in the world and then got humbled all throughout bowl season.” We did a whole Shutdown Fullcast episode about that one.

Q: Are you also doing a series on the bloodiest Blood Weeks ever for each point in a season throughout college football history, and will you add each new episode here as they release?

Yes, here is Week 1, when #1 Miami lost to BYU’s punter to begin 1990:

And here’s a September digest (since September is usually lighter on mayhem), featuring 1974, 1984, and 2008:

Followed by mid-October, featuring a sprint through 1978, 1981, 1990, 1993, 2003, 2017, and 2018: