While prohibited under civil law, polygamous marriages may be performed under the nation's customary law, which the government officially recognizes in compliance with the Customary Marriage Act. An estimated 10% of Zimbabwean adult women are in polygamous marriages.
Where the girlfriend or partner is not recognised as married to the polygamous man, either because the man is married under civil law or because no customary marriage has been performed, she is often referred to as a 'small house'.
References
Polygamy in Zimbabwe Wikipedia(Text) CC BY-SA