expression
seriously; joking aside; in all seriousness
Used to preface a sincere statement, often after a lighthearted exchange, to signal that what follows is meant earnestly.
冗談抜きで、本当に助かったよ。
Seriously, you really helped me out.
冗談抜きで、その話はやめたほうがいい。
Joking aside, you'd better drop that topic.
Means 'seriously' or 'earnestly' as an adverb, but lacks the 'joking aside' nuance; 冗談抜きで explicitly sets aside prior joking.
Compound of 冗談 (joke) + 抜き (omitting, without) + で (particle), literally 'without jokes'.