He walked around with his camera slung around his neck.

slung 是动词 sling 的过去分词形式。sling 的意思是"悬挂、吊挂"，通常指用带子或绳子将物品悬挂在身体某个部位。slung around the neck 表示"挂在脖子上"的这种悬挂方式。