英语中，表示“他走不快”可以说 "He doesn't walk quickly"。例如：
He doesn't walk quickly, so we always have to wait for him.
翻译：他走不快，所以我们总是要等他。
He doesn't walk quickly, but he makes up for it with his endurance.
翻译：他走不快，但他用他的耐力来弥补。
该表达的来源是英语中的动词 "walk"（走路）和副词 "quickly"（快地）。"He doesn't walk quickly" 的意思是“他走路不快”。