The thousandth item in a series is the one that you count as number one thousand.
双语例句
例：
The magazine has just published its six thousandth edition.
这本杂志刚刚出版了第六千期。
2.?第一千（强调某事发生的次数非常多）
If you say that something has happened for the thousandth time, you are emphasizing that it has happened again and that it has already happened a large number of times.
双语例句
例：
The phone rings for the thousandth time.
电话铃响了一千次了。
NOUN. 名词
thousandths
1.?[C 可数名词] 千分之一
A thousandth is one of a thousand equal parts of something.
双语例句
例：
a dust particle weighing only a thousandth of a gram.