The 'Book Shelf' Speakers that I was looking at to buy, refer to the speakers as 'Loudspeakers' simply because it has an amplifier added to or built within the encasement of the speakers. That implies that this particular type of speaker has the advantage of amplifying whatever sounds it receives.
I therefore conclude that 'Loudspeaker' is too ambiguous & can't really be defined in the strictest sense. It neither refers to a device that aids or projects the human voice, nor can it be referred to as a device that produces sound via an electrical signal converter & it certainly doesn't have anything to do with high wattage resolution, for all of those things are usually already stated in the Specs, as a selling point.
If anything, 'loudspeaker' is just an additional descriptive term that denotes a 'speaker'. It is done so for the purposes of marketing the product. It can't be specified on the product detail listing or page because there are no mathematical equations or scientific rules to follow what constitutes as being a 'loudspeaker'.