Sorry, it's not really an english thing, it's mapping language. Yes, it's dynamic entities. They use up edicts (some hammer entities use more than one edict). The limit is 2048 and if you reach it the server will crash.
Pipeline as a map uses up approximately 1450 edicts leaving the rest for run-time entities like players and their weapons. It is possible to crash pipeline with enough players shooting stickies, but valve seems to think it alright. I would assume it is still safe with the new higher sticky limit. Though I suppose we'll see if valve updates pipeline or not.