The Collaborative International Dictionary of English v.0.48:
lowerclassman \lowerclassman\ n. an undergraduate who is not yet a senior. Syn: underclassman. [WordNet 1.5]WordNet (r) 3.0 (2006):
lowerclassman n 1: an undergraduate who is not yet a senior [syn: lowerclassman, underclassman]