TL;DR: Is it possible to define hierarchy, as a useful term for communication and association between anarchists? If so, what are some of those definitions?
There are many different strains of anarchism, and specially since anarchists mostly believe in decentralization, I feel like many of our efforts go diluted for lack of collective organization. Sure, there are big anarchist collectives doing work out there, but I have the sensation that most youth or influential people who identify themselves with anarchist causes get lost in the plot simply for lack of a bigger movement. For most of the modes of anarchism there is one big bad evil guy, commonly named "hierarchy"; although writers and academics define those terms in their publications, I can't help but notice, at least in the forums I've been around, your average anarchists could be talking about two completely different concepts of hierarchy or oppression. Maybe if we had agreed upon definitions to those hot topics it would be easier to associate. Is that even possible? That we all agree on the same meaning for a word? Do we call Chomsky to solve this linguistical issue?
Or am I completely wrong in my questionings?
I think this is a good start, but still too little rigid. This definition still requires one to define Systems of Domination or institutions of subordination. The examples are a big help, but it is still unclear what falls under those categories.
Do unions fall under those "institutions of subordination"? As an example of ambiguity under this definition.
I laud the curiousity. Unions are diverse and within even one union exists dozens or hundreds of 1:1 relationships as well as collective overlapping interests. My summary answer thus is: No, on their own, unions are not an institution of subordination, particularly given the alternative (subordination to the boss/baron/owner), but a complete picture requires an Anarcho-Relationship lense (see the honeycomb video)
And that's a good answer, but I argue it is to the detriment of the definition that this needs to be answered. Maybe there is a better way to define hierarchy, or a simple definition for "systems of domination or institutions of subordination" that could be given along side that already answers that.