Altisonant is an adjective that means lofty or pompous. 

The Latin prefix A-L-T-I comes from ‘altus’ (AWL toose) meaning high, as in ‘altitude’ or ‘alto.’ Sonant (SEW nant) means ‘sound.’ Since the 16th century, altisonant has been used by English speakers to describe someone who sounds ‘high and mighty.’ Here’s an example:

Rex can get a little big for his britches from time to time. Most of the time, he’s a fairly down-to-earth fellow, but when he starts referring to himself in the third person, you know he’s about to get altisonant.