%monoptote%

n. [ L. monoptotum, Gr. mono`ptwtos; mo`nos single + &unr_; apt to fall, fallen, fr. &unr_; to fall; cf. &unr_; case. ] (Gram.) 1. A noun having only one case. Andrews. [ 1913 Webster ]

2. A noun having only one ending for the oblique cases. [ 1913 Webster ]