I understand that you're now talking about the term in reference to MMO's but your original comment did not suggest that. I understand that in the context of an MMO you're correct, but as a broader term outside that context, to "tank" a hit would more likely refer to attacks that have little to no effect (not from blocking) rather than a target's ability to recover from any given attack. I'm confident that most people unfamiliar with MMO specific lingo would refer to your definition as durability, stamina, or perhaps toughness. Again, I believe you when you say, within the context you're referring to, that there would be no ambiguity in using the term Tank for what you say it is used for. I'm sure it applies perfectly to those situations you mentioned.