21. A non-transitory computer storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising: determining that a plurality of addresses cannot be geocoded by a geocoding system, wherein each address includes a plurality of terms; generating a plurality of variants of the addresses that can be geocoded by the geocoding system, wherein each variant of a respective address lacks a removed term included in the respective address; receiving a plurality of name terms for each variant provided by the geocoding system; associating each removed term with name terms received for all variants that lack the removed term, including determining, for each associated name term of each removed term, a count of the number of variants for which the geocoding system provided the name term; determining, for each associated name term of each removed term, whether the name term is an address term synonym for the removed term based at least in part on the count of the number of variants.
21. A non-transitory computer storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising: determining that a plurality of addresses cannot be geocoded by a geocoding system, wherein each address includes a plurality of terms; generating a plurality of variants of the addresses that can be geocoded by the geocoding system, wherein each variant of a respective address lacks a removed term included in the respective address; receiving a plurality of name terms for each variant provided by the geocoding system; associating each removed term with name terms received for all variants that lack the removed term, including determining, for each associated name term of each removed term, a count of the number of variants for which the geocoding system provided the name term; determining, for each associated name term of each removed term, whether the name term is an address term synonym for the removed term based at least in part on the count of the number of variants. 29. The computer storage medium of claim 21 , wherein the geocoding system is configured to geocode addresses having missing terms.