"低下头"是指把头低下来或者俯视着看。在英语中，这个动作可以用 "lower one's head" 或者 "look down" 来表示。
"Lower one's head" 来源于动词 "lower," 意思是使某物沿着直线向下移动或向下倾斜。因此，"lower one's head" 就表示把头向下倾斜。
举个例子：
She lowered her head as she walked past him, not wanting to make eye contact. (她走过他时把头低下来，不想和他目光对视。)
"Look down" 来源于动词 "look," 意思是注视某物或者向某个方向看。因此，"look down" 就表示向下看。
举个例子：
He looked down at his feet as he spoke, feepng embarrassed. (他在说话时向下看自己的脚，感到尴尬。)