Incomprehensible; fathomless; inscrutable.
Opaque; obscure; not translucent or transparent.
Not penetrable.
A person not openly given to friendship.
Being, or having the salient properties of, a monotone function.
Having a single unvaried pitch.
A piece of writing in one strain throughout.
A single unvaried tone of speech or a sound.
To speak in a monotone.