underclassman

[ uhn-der-klas-muh n, -klahs- ]
/ ˌʌn dərˈklæs mən, -ˈklɑs- /

noun, plural un·der·class·men.

a freshman or sophomore in a secondary school or college.

Origin of underclassman

An Americanism dating back to 1870–75; under- + class + -man