Definitions for "LDU"
Keywords:  udl, sortation, fsa, postal, delivery
loop diagnostic unit
Local Defense Units
Local delivery unit. The last three characters of a postal code which denote a very small and easily defined section within an area described by the FSA. These characters can specify one side of a city block, an apartment building, an office building or a large firm or organization which does considerable business with the Post Office. They can also denote service from a post office or postal station.