unprepared
ad lib
ad libitum
ad-lib
archaic
casual
caught napping
caught off balance
caught short
extemporal
extemporary
extempore
extemporized
haphazard
hasty
impromptu
improvisatorial
improvise
improvised
improviso
impulsive
informal
jury-rigged
makeshift
off the cuff
off-the-cuff
offhand
precipitate
qualifier
rough-and-ready
snap
spontaneous
spur-of-the-moment
stopgap
surprised
taken aback
taken by surprise
taken unawares
tripped up
unarranged
unbegun
unconcocted
uncontrived
undeliberated
undevised
unhatched
extemporaneousness
extemporize
Gaelic
after-dinner
aphasic
choral
edify
epigrammatic
expository
fervid
fluent
glib
heart-stirring
idiomatic
impassioned
inaugural
inspirational
introductory
long-winded
motivational
prefatory
self-forgetting
unfettered
unpremeditated
valedictory