cihuanemactli.

Motolinia describes these as women who were given to nobles as secondary wives. There were not married to the men in a full ceremony. This practice was viewed as more legitimate than concubinage (or momecatiliztli, literally, "tying oneself" to someone).
Louise M. Burkhart, Before Guadalupe: The Virgin Mary in Early Colonial Nahuatl Literature, Institute for Mesoamerican Studies Monograph 13 (Albany: University at Albany, 2001), 50.