adverb
(not) at all; (not) in the least; (none) whatsoever
Used with a negative verb to emphasize complete absence or denial. Stronger than 全然.
そんなことはさらさら思っていません。
I don't think that at all.
彼に会う気はさらさらない。
I have absolutely no intention of meeting him.
Reduplication of 更 (さら), an old word meaning 'again' or 'more', with the reduplication intensifying the negative sense to 'not even a bit more'. The exact historical development is uncertain.