immūtesco — Lewis & Short
immūtesco (inm-), tŭi, 3,
I v. inch. n. [in-mutesco], to become dumb or speechless (post-Aug.):
immutescamus alioqui, si nihil dicendum videatur,Quint. 10, 3, 16:
ruptis ore querelis,Stat. Th. 5, 542.