`<boost/unordered/unordered_map.hpp>` Synopsis :idprefix: header_unordered_map_ Defines `xref:reference/unordered_map.adoc#unordered_map[boost::unordered_map]`, `xref:reference/unordered_multimap.adoc#unordered_multimap[boost::unordered_multimap]` and associated functions and alias templates.