at a moment's notice
instanter
incontinent
forthwith
at the drop of a hat
immediate
on the nail
in the blink of an eye
in the twinkling of an eye
right now
right
all of a sudden
in the wink of an eye
presently
tout de suite
most Rikki-Tik
immediately
offhand
right off
instantaneously
in a flash
tatkal
unhesitantly
instant
like a shot
at one stroke
at once
spontaneous
insta-
soonest
proximally
straight away
off the rip
right away
off the bat
this instant
flash
straight out of the chute
stat
⠊⠍⠍
as soon as look at someone
suddenly
warningless
this minute
straightly
in a jiffy
sudden
instantiable
on the spot
out of the chute