应该是zip code，邮政编码。
美国邮政编码 (英语：ZIP Code）是美国邮政使用的一种邮政编码，一般常以大楷写作ZIP。ZIP是英语：Zone Improvement Plan （地区改进计划）的简称，它暗示邮件可以以更有效率及快捷地送到目的地。最基本的ZIP编号包括五个号码，随后增加了四个号码，使邮件可以更精确地传送到目的地。增加号码后的ZIP编号称为”ZIP+4″。ZIP编号曾被美国邮政注册成一个商标，但其注册至今已经过期。
以下是英文版的解释
ZIP Codes range from 00501, belonging to the Internal Revenue Service in Holtsville, NY, to 99950 in Ketchikan, AK. Easiest to remember? How about 12345, a unique ZIP Code for General Electric in Schenectady, NY.
Quick! What’s that ZIP Code?
The ZIP Code was introduced in 1963. The first number represents a general geographic area of the nation, “0” in the East moving to “9” in the West. The next two numbers indicate regional areas and the final two, specific Post Offices or postal zones in larger cities. Make it a ZIP+4 Code, introduced in 1983, and mail can be sorted to specific streets, buildings, houses and businesses. Today, ZIP Codes are important parts of the nation’s 911 emergency system. ZIP = Zone or Zoning Improvement Plan.
