That may seem an almost silly question to ask. I mean, duh
An organism is such a common concept that it can be taken for granted, no?
But, I'm hard pressed to give a good or robust definition, and Bloom doesn't provide a definition for me (at least not in the pages I've read so far); yet it seems a critical thing to understand given the fact that he lists the superorganism as concept number two
in his list of the foundations underlying the Lucifer Principle.
I might attempt this def: An organism is a living entity.
But that begs the questions: What does it mean to be living? And, what does it mean to be an entity? (This is where things delve into stuff like complex adaptive systems and the identity of an organism.)