A lot of people get bent out of shape when I use the word "denomination" in reference to Eastern Orthodox churches or the Roman Catholic Church. They like to claim that they don't have denominations and that "denominations" are a Protestant thing.
Taking the dictionary definition straight up, they don't have an argument. PECUSA is a denomination, and OCA is a denomination, and ROAC is a denomination, and the Catholic Church is a surpassingly large denomination. The word denotes organizational units, and connotes a difference in "flavor". Objectively, it is almost trivial to draw lines between these groups.
So why do people protest? Because they want to slant the playing field in the direction of claiming that their (generally Eastern Orthodox or Catholic) church is a totally different kind of fish from a Protestant body. I'm not the least convinced-- not because I'm presuming that they are all parts of The One True Church, but because on an earthly level they obviously are different species of fish-- but all are fish.
In other contexts the constant battle over the word gets to be a waste of time and I fish for other words to describe the likeness of ROAC and ECUSA. Here I'm more interested in how the argument is carried forth, so I'll stick with "denomination", thank you.