adverb
(not) even a little bit; not in the slightest
Used with a negative predicate to emphasize that something is completely absent or not at all the case. Literally 'not even a dewdrop's worth'.
彼の言葉には露ほどの真実もなかった。
There wasn't even a shred of truth in his words.
私は露ほども疑っていなかった。
I didn't doubt it in the slightest.
少しも is a more common and neutral way to say 'not at all' or 'not even a little', while 露ほど is more emphatic and literary, often used in negative sentences for strong denial.
Compound of 露 (つゆ, 'dew') + ほど ('extent, degree'), literally 'even the amount of a dewdrop'. Used idiomatically with negatives to mean 'not even a little'.