"subtler" in the adjective sense
1. elusive, subtle
difficult to detect or grasp by the mind or analyze
"his whole attitude had undergone a subtle change"
"a subtle difference"
"that elusive thing the soul"
able to make fine distinctions
"a subtle mind"
3. insidious, pernicious, subtle
working or spreading in a hidden and usually injurious way
"glaucoma is an insidious disease"
"a subtle poison"
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License