hippopotomonstrosesquipedalian /ˌhɪpəˌpɒtəˌmɒnstɹəˌsɛskwɪpɪˈdeɪlɪən/ adjective1 •Of or pertaining to extremely long words.To indulge in hippopotomonstrosesquipedalian tergiversation is not to show your erudition: rather, it is to be superficial. — 1997 formsmore hippopotomonstrosesquipedalian · most hippopotomonstrosesquipedalian