medial adj. 1 a situated in the middle. b (of a letter etc.) occurring in the middle of a word or between words. 2 of average size. ♦ medially adv. [Late Latin medialis from Latin medius middle]
I looked this up because of the popular practise of smushing two words together and capitalizing them both, like PlayStation or CinemaScope. I knew there was a word for this, but I couldn’t find it. The closest I came was the name of that second capital letter. Medial capital.
Definition courtesy of The Canadian Oxford Dictionary, 1998.