We can define it any number of ways. Any load that approaches maximum in the loading manuals is a hot load. Once the load reaches or exceeds max, its probably too hot.

And any load that shows pressure signs is hot. I say too hot, but what do I know. If the case is hard to extract (or won't), if the primers are protruding or flattened, if the case just forward of the rim has expanded, if the case necks are splitting in otherwise good condition brass.

The goal of handloading is to make safe and economical loads. When you push that beyond what factory loads deliver, its at least hot, probably too hot.

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Dick Burg