From Longman Dictionary of Contemporary Englishsophomoricsoph‧o‧mor‧ic /ˌsɒfəˈmɒrɪk◂ $ ˌsɑːfəˈmɔːrɪk◂, -ˈmɑː-/ adjective American English formal STUPID/NOT SENSIBLEsilly, and behaving in a way that is typical of someone much younger sophomoric humor
Examples from the Corpus
sophomoric• This has got to be one of the most embarrassing film moments of the year -- sophomoric, self-congratulatory and stupid.• a sophomoric sense of humor 