excursus
Concise Oxford English Dictionary © 2008 Oxford University Press:
excursus /ɪkˈskəːsəs, ɛk-/
▶noun (pl. same or excursuses) a detailed discussion of a particular point in a book, usually in an appendix.
■ a digression in a text.
– origin C19: from L., ‘excursion’, from excurrere ‘run out’.
'excursus' also found in these Oxford entries:
