in·ex·pres·sive /-ˈsprɛsɪv/
(a.)無表情的
In·ex·press·ive a.
1. Inexpressible. [R.]
2. Without expression or meaning; not expressive; dull; unintelligent; as, an inexpressive countenance.
◄ ►
inexpressive
adj : not expressive; "an inexpressive face"