He described the movie very prosaically, mentioning only the plot and its duration.

prosaically 是形容词 prosaic 的副词形式。prosaic 来自名词 prose（散文），加上形容词后缀 -aic 构成，本义是"散文般的"，引申为"平淡无奇的、缺乏想象力的"。prosaically 表示"以平淡无奇的方式"。