Definition
Academic discourse, which is historically grounded, includes all lingual activities associated with academia, the output of research being perhaps the most important. The typicality of academic discourse is derived from the (unique) distinction-making activity which is associated with the analytical or logical mode of experience.
(Patterson & Weideman 2013).
Explanation
Academic discourse is more than grammar; it has functions like exposition, clarification, and conclusion, requiring us to do things with language like explain, define, compare, contrast, classify, agree, disagree, illustrate, elaborate, make claims, see implications, infer, exemplify, anticipate, and conclude. In addition, imbued as it is with cognitive as well as analytical processing, competence in handling academic language is far more than the ‘skills’ of listening, speaking, reading, and writing …
Weideman 2018
The ability to handle this complex kind of language has at its centre the idea of using language in a logically qualified way: to make theoretical distinctions and for the purposes of analysis. Therefore the measurement of the ability must encompass many sub-components, to do justice to the complexity of the language ability being assessed. It follows, too, that a language test that is multifaceted is preferable to a monotone test design, and is likely to be more reliable. The same would apply to language courses to develop academic literacy, as the ability to handle academic discourse is usually termed.
Click to find Albert Weideman’s definition of academic literacy.
References
Patterson, Rebecca & Weideman, Albert . 2013. The typicality of academic discourse and its relevance for constructs of academic literacy. Journal for Language Teaching, 47(1): 107-123.

Weideman, Albert. 2018. Academic literacy: why is it important? Introduction to Academic literacy: Five new tests. Bloemfontein: Geronimo, pp. iii-x.