IPA: /ˈʌndərˌklæs.mən/
KK: /ˈʌndərˌklæs.mən/
A student who is in the first or second year of high school or college.
As an underclassman, she was eager to learn from her older classmates.
Underclassman → It is formed from "under-" (meaning beneath or lower) and "classman" (from "class" meaning a group or category, and "man" meaning a person). The term refers to a student who is in a lower class or year in school compared to upperclassmen.
Think of someone who is 'beneath' ('under-') in rank or year compared to others in their 'class' — that's why an underclassman is a student in a lower grade.
No commonly confused words.