He flipped through the documents on the desk desultorily, not focusing on his work at all.

desultorily 是副词，由形容词 desultory 加副词后缀 -ly 构成。desultory 来自拉丁语，原意是"跳跃的、不连贯的"，引申为"随意的、无目的的"。desultorily 在这里形容翻看文件时"漫不经心、毫无目的"的状态。