Inscrutable

[Sarah]

Unsearchable; incapable of being searched into and understoodby inquiry or study; impossible or difficult to be explained oraccounted for satisfactorily; obscure; incomprehensible; as, aninscrutable design or event.'T is not in man To yield a reason for the will of Heaven Which isinscrutable. Beau.

[Sarah]

If a person or their expression is inscrutable, it is very hard to know what they are really thinking or what they mean.

[Sarah]

An inscrutable girl is one who'll [make out], but not put out.

[Lizzy Liz]

not showing emotions or thoughts and therefore very difficult to understand or get to know:

[Magaret]

Impossible to understand or interpret.