It means that it belongs to another and that it is not mine or ours. Strange, foreign, improper. Agena, thus, with g, is the name of a latin star also called in Arabic Hadar, which corresponds to knee (that of the horse or centaur). It belongs to the constellation Centaurus (Centaurus).
* Only one "like" per meaning and day, the more "likes" the meaning will appear higher in the list