What exactly is a "SPUN" bearing?

[Helluvarush]

I see a lot of trackicks for sale around here,and seems to be a pretty common theme. " ran good,spun a bearing, $800 obo" . I'm starting to think that's what people say when they aren't sure what's wrong with it. So what EXACTLY is a spun bearing,from the sound of it,I would surmise it has somehow spun a Journal bearing in a way that has denied oil to the mating surface,letting friction and all hell run rampant. I ask,because I bought my second kick 3 days ago,"with a bent rod", so I go through the motions,check crank cam timing, do a leak down test,adjust the valves, everything is good up to this point. And let me say this,this is by far the cleanest engine I've seen in an 4wd vehicle from the early 90s,it looks exceptionaly well maintained, no missing nuts and bolts, undercarriage has VERY little rusting just a couple spots. No dirt or oil buildup.intake manifold is spotless inside with the typical dull aluminum exterior. Point to all this is coming,I check the oil,W.T.F.?! it has 8 qts in it! Actually 7.75,but 8 sounds better to the story. I'm thinking maybe that's caused the "knock" the PO was telling me about,so I decided to just take the motor out and go over it completely. Enter the "SPUN" bearing. Or lack there of.....piston #4 has no bearing,not a trace of one at all,no metal pieces,no powder no shavings I've looked everywhere and it doesn't exist. I'm thinking they had it rebuilt,and for whatever reason they just decided " ya know what,we've got this far in the rebuild,let's just close it up and let it ride". Has anyone ever spun a bearing in a way it just disappeared, without causing damage to the cylinder walls or anything else.I mean the connecting rod was still torqued to spec,but OBVIOUSLY very loose fitting on the crank. I'm really at a loss how that could happen other than negligence, but maybe one of you have had one of these elusive spun disappearing bearings.[/size]