adjective subtler sub′·tler (-lər, -'l ər), subtlest sub′·tlest

1. thin; rare; tenuous; not dense or heavy a subtle gas
2. 1. capable of making or noticing fine distinctions in meaning, etc. a subtle thinker
   2. marked by or requiring mental keenness subtle reasoning
3. delicately skillful or clever; deft or ingenious a subtle filigree
4. not open or direct; crafty; sly
5. delicately suggestive; not grossly obvious a subtle hint
6. working insidiously; not easily detected a subtle poison

Etymology: ME sotil < OFr soutil < L subtilis, fine, thin, precise, orig., closely woven < sub- (see sub-) + tela, web < *texla < texere, to weave: see technic