Martin Filler

The first half of the 1960s was the apogee of what might be termed the Age of Cool - as defined by that quality of being simultaneously with-it and disengaged, in control but nonchalant, knowing but ironically self-aware, and above all inscrutably undemonstrative.

American Critic

Used when someone's feelings or thoughts are completely hidden, often causing confusion or curiosity.

Unreadable Emotions

Describes situations where the outcome or meaning is unclear and leaves room for interpretation.

Ambiguous Situations

Be aware that expressions might seem inscrutable due to cultural differences in communication styles.

Inscrutably