IPA: //ˈsuːpərˌsʌtəl//
KK: /ˈsuːpərˌsʌtəl/
Extremely delicate or fine, to the point that it is difficult to notice or perceive.
The artist's use of color was so supersubtle that only the keenest observers could appreciate it.
Supersubtle is formed from "super-" (meaning above or beyond) and "subtle" (from Latin "subtilis", meaning fine or delicate). The word describes something that is extremely fine or delicate, going beyond what is typically subtle.
Think of something that is 'beyond' ('super-') fine or delicate ('subtle') — that's why supersubtle means extremely fine or delicate.