magniloquentadj.

magniloquent (adj.)1650s, a back-formation from magniloquence, or else from Latin magniloquentia "lofty style of language," from magniloquus "pompous in talk, vaunting, boastful," from comb. form of magnus "great" (see magnate) + -loquus "speaking," from loqui "to speak" (see locution).