When I asked which of "ungrammatical" or "grammatically incorrect" is prefered and why? at an English language forum I got the following "linguistic perspective":
Both are used, but I believe linguists prefer the former. Grammaticality, as one linguist explained it to me, means "following the rules of the relevant scientific model that is used to describe how people speak". So it is strictly dependent on the model used, but in practice many linguists presume that there is consensus about most elements of the relevant model, so it mostly overlaps with "people actually use this within a certain group and they consider it normal".
The word "incorrect" may suggest that there is something wrong with straying from grammatically; I suspect that linguists do not use this much because they resent the implication. So I think that's why you will mostly see ungrammatical.
Could you please comment on the linguistic accuracy of this answer?