IPA: /ɪnˈskruːtəˌbɪlɪti/
KK: /ɪnˈskrutəˌbɪlɪti/
The quality of being difficult to understand or interpret; something that is mysterious or not easily figured out.
The inscrutability of her expression made it hard to know what she was thinking.
Inscrutability is formed from "in-" (meaning not) and "scrutari" (meaning to search or examine) and the suffix "-ability" (meaning the quality of being). The word describes the quality of being impossible to search or examine, hence, something that cannot be understood or interpreted.
Think of 'not' ('in-') being able to 'search' ('scrutari') something — that's why inscrutability means something that cannot be understood.