It means something like a kind of dulled grayness or ordinariness of life.

它代表着一种,生活的灰暗，单调。

耶鲁公开课 - 文学理论导论课程节选

He described provincials as being dominated by routine and monotony in their small towns, that they're all the same, he wrote, which is obviously not the case.

他把乡下人描绘成在小城镇中,过着千篇一律的单调生活,他写道,他们全是一个模子里刻出来的,情况显然不是这样

耶鲁公开课 - 1871年后的法国课程节选