Lewis Short
(adj.adv.) : in-dēclīnābĭlis, e, adj.
* Inflexible, unchangeable, only in a trop. sense (postAug.).
* In gen., of things: virtus animum rectum et indeclinabilem praestat,Sen. Ep. 66: justitia,id. ib. 74: series re rum,Gell. 6, 2.—Of persons: judex,Amm. 25, 4; id. 18, 1.
* In gram.: nomen, indeclinable, Diom. pp. 288, 289 P. — Hence, indēclīnābĭlĭter, adv., unchangeably, Aug. Civ. Dei, 9, 22 fin.
Charlton T. Lewis, Charles Short, A Latin Dictionary