On the most basic level, the gender liminality theory for Byzantine eunuchs is the idea that an in-between gender identity for eunuchs could be subconciously expanded by people in their society to give them a larger in-between or go-between social role, and that this worked on many levels. Liminality is a much larger theory though, and the liminal gender theories certainly aren’t limited to Byzantine eunuchs, it works for many “third gender” categories in other socieities, and it works gosh darned well for other court eunuchs too. (The only eunuchs it doesn’t really work for is the Italian castrati, amusingly enough, as they probably didn’t have a strong “outsider” gender identity or social role.)

From the introductory chapter of The perfect servant : eunuchs and the social construction of gender in Byzantium

Given both modern assumptions and the persistent ambiguity associated with eunuchs in our sources, it is hardly surprising that the question has been raised as to whether and, if so, in what ways, Byzantine eunuchs were marginal members of their society. In the course of this discussion three terms - liminality, marginality, and gender - tend to surface and interact. Eunuchs were certainly liminal if we use this term in its most literal sense, since they operated across thresholds or boundaries. In the course of this study we will see eunuchs cross social, spiritual, and gender boundaries. I would suggest, however, that despite first impressions, eunuchs were not marginal to society in economic, spiritual, or political terms. Rather, they were marginal in the sense that they did not fit easily into a bipolar gender structure. Their existence forced people to talk about them using a language that lacked a convenient vocabulary.They made their contemporaries uneasy because they were seen to move too readily between the worlds of men and women, between earthly sensuality and heavenly spirituality, between imperial presence and ordinary space, and between the church and the secular world.

Good summary I think!

Out of curiousity, where’d you run into this term?