impromptus — Lewis & Short
impromptus (inpr-), a, um. adj.2. in-promptus,
I not ready, not quick (rare):
infacundior et lingua impromptus,Liv. 7, 4, 5:
imprompto jam Arminio ob continua pericla,Tac. A. 2, 21:
sermone impromptus Latio,Aus. Idyll. 2, 9.