Lewis & Short

in-strĕpo, ŭi, ĭtum, 3, v. n., to make a noise anywhere; to sound, resound, rattle, clatter, creak (mostly poet. and post-class.): sub pondere faginus axis Instrepat, * Verg. G. 3, 172: dentibus, to gnash, Claud. Cons. Mall. Theod. 222.
With a Gr. acc., to make resound, to utter: lamentabiles questus, App. M. 2, p. 126, 36 (but in Liv. 4, 43 fin., the correct read. is increparet).