noun, noun or participle which takes 'suru', transitive verb
Formal, literary term for forming a guess or hypothesis based on limited evidence. Often used in the expression 端倪すべからず (unfathomable, beyond conjecture).
彼の真意は端倪すべからざるものがあった。
His true intentions were beyond conjecture.
この問
The solution to this problem is not something that can be easily surmised.