The lowest female singing voice WordNet 3.0 & Open English WordNet

A contralto is a type of classical singing voice whose vocal range is below that of the mezzo-soprano. Wikipedia

Type of classical female singing voice Wikidata

The lowest female singing voice. OmegaWiki

The lowest female voice or voice part, falling between tenor and mezzo-soprano. The terms contralto and alto refer to a similar musical pitch, but among singers, the term contralto is reserved for female singers; the equivalent male form is counter-tenor. Originally the contratenor altus was a high countermelody sung against the tenor or main melody. Wiktionary

The lowest female voice. Wiktionary (translation)