The Collaborative International Dictionary
Diptote
Diptote \Dip"tote\, n. [Gr. ?; di- = di`s- twice + ? falling,
fr. ? to fall: cf. F. diptote.] (Gram.)
A noun which has only two cases.
--Andrews.
Wiktionary
diptote
n. (cx grammar English) In grammar, a noun which has only two case. In Modern Standard Arabic, nouns belong to triptote or diptotes, or can be indeclinable.