LATIN DICTIONARYLexicon Latīnum
adjectivefirst/second-declension adjective (nominative masculine singular in -er)

improsper

improsper (feminine improspera, neuter improsperum, adverb improsperē)
Classical[ɪmˈprɔs.pɛr]Ecclesiastical[imˈprɔs.per]

Meaning

  1. adjectiveunfortunate, unprosperous

Declension

singular
formmasculinefeminineneuter
nominativein -er
improsper		improsperaimprosperum
genitiveimprosperīimprosperaeimprosperī
dativeimprosperōimprosperaeimprosperō
accusativeimprosperumimprosperamimprosperum
ablativeimprosperōimprosperāimprosperō
vocativeimprosperimprosperaimprosperum
plural
formmasculinefeminineneuter
nominativeimprosperīimprosperaeimprospera
genitiveimprosperōrumimprosperārumimprosperōrum
dativeimprosperīsimprosperīsimprosperīs
accusativeimprosperōsimprosperāsimprospera
ablativeimprosperīsimprosperīsimprosperīs
vocativeimprosperīimprosperaeimprospera

improsper (inpr-), spĕra, ĕrum, adj. 2. in-prosper,
I. unfortunate, unprosperous (post-Aug.): fortuna, Tac. A. 3, 24: moles insidiarum, id. ib. 14, 65: multa claritudine generis sed improspera, id. ib. 4, 44.—Adv.: improspĕrē, unfortunately: cessit, Col. 1, 1, 16; Tac. A. 1, 8; Gell. 9, 9, 12.

Origins

  1. Proto-Indo-European*né
  2. Proto-Indo-European*n̥-
  3. Proto-Italic*n̥-
  4. Latinimprosper

Latin prosper Latin improsper From in- (“un-”) + prosper (“prosperous, favourable”).

Quick answers

What does improsper mean in Latin?
improsper, a adjective, means “unfortunate, unprosperous”.
How do you pronounce improsper?
In classical Latin, [ɪmˈprɔs.pɛr]; in ecclesiastical (church) Latin, [imˈprɔs.per].
Where does improsper come from?
Proto-Indo-European *né → Proto-Indo-European *n̥- → Proto-Italic *n̥- → Latin improsper.