Monotonously; adjective; lacking in variety, tediously unvarying.

From The Shawl by Louise Erdrich: “If she could have thrown off that wronghearted love, she would have, but the thought of the other man, who lived across the lake, was with her always. She became a gray sky, stared monotonously at the walls, sometimes wept into her hands for hours at a time.”

After searching this word, I now understand that the narrator described the women as boring, having no variety or activity. She had become flat.