All rather meaningless as the term is not defined strictly in terms of botany or zoology. Wiki and OED are not what governs strict taxonomical use: they merely summarize some ways in which it is used.
I asked our fastidious taxonomist and got the following:
Are these regulated taxonomic ranks or groups?
See also: https://species.nbnatlas.org/species/NHMSYS0000869662#names
And got this:
From: RiaaN StalS
Sent: 20 August 2017 03:26
To: Tony Rebelo
Subject: Re: groups versus aggregates
A. Short and sufficient answer:
Neither "aggregate" nor "group" is regulated (or indeed recognised as a taxonomc rank) by any of the three codes that I have a grasp of.
B. Medium-boring answer:
"Group" is a useful and easily abused term that may refer to any conglomeration of taxa at any rank that are referred to as ... well ... as a group. "Group" is an informal categorisation without defined circumscription which is used because it may be useful, but which is bound to differ over time and among groups of speakers.
"Group" on its own needs not have any phylogenetic meaning (i.e. needs not to be monophyletic, or even meaningful in any evolutionary manner). Some wild such examples would be "the group of warm-blooded vertebrates" or "the purple daisy group" or the "antelope group with horned females".
"Group" may, on the other hand, be useful and even phylogenetically sensible/defensible, e.g. as in "species groups" within a genus-group taxon, or "genus groups" within a family, etc. These would preferably each be monophyletic, but in real life they most often are not. As handles and tools they are, however, frequently very useful. In large genera with unknown phylogeny such "species groups" are ubiquitous, and most often really useful.
You may ask why such a "group" is not rather ranked as a subgenus or similar, to which I can only say that
(a) I do not know, it's a historical thing;
(b) it's better not to place such groups of convenience in formal taxonomic groups when their monophyly is unproven.
I've first seen or heard of "aggregate" only on iSpot and, from there, in the sources that feed iSpot, like NBN. I've never understood it. I found an attempt at a definition in a completely odd but entirely useful GBIF document, authored by one of the greatest living mavericks in biology, O.B.E.
(What the heck, let me attach the document. I've actually been keeping it from you since forever, because you are a maverick also and the book irreverent. Many of the ideas therein are rather peculiar, much like some of your ideas. I'm going to regret this gift in future.)
There is no logical relation between "group" and "aggregate", for the reasons both that they are not robustly defined epistemologically or operationally; and because they have no necessary phylogenetic content.
C. Comprehensive answer:
Don't even get me started. You don't have enough time, I may project. Or I may allege not to share my pearls of mind with a paraphyletophiliac. The take-home message is that "aggregate" and "group" are terms that look for trouble, and should be avoided when not explicitly defined in every single instance. Even retrospectively defined for the many "groups" of anything in the heritage literature.
• That Hungarian congress abstract is superb reading. Yeah, the carnea problem does not go away. Perhaps it's not a problem, but a challenge, in the Zumian sense.
• All these comments are CC BY 3.0 ZA. I don't want to become involved in the forums at this stage. Except for the dictionary update forum, for which I have a thick ream of things pending.
Cheers. Thanks for cheering me up.