IPA: /ˌɪnɪkˈsprɛsɪvli/
KK: /ɪnˈɛkspresɪvli/
In a way that shows no feelings or emotions; without any expression on the face or in behavior.
She stared inexpressively at the painting, showing no reaction to its beauty.
Inexpressively → It is formed from "in-" (meaning not), "express" (from Latin "expressus", meaning to press out or convey), and "-ively" (meaning in a manner of). The word means in a manner that does not convey emotion or feeling.
Think of 'not' ('in-') conveying something ('express') — that's why inexpressively means not expressing feelings.