sophomore

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A second-year student in a US college.
• noun A tenth-grade student in a US high school.
• noun A person in the second year of carrying out an endeavor.
• noun A three-year-old racehorse, usually in its second year of racing.
• adjective Of or relating to the second year of an endeavor, especially of attending a school or college.
• adjective Being the second in a series.

from The Century Dictionary.

• noun A student in the second year of his college course.
• Pertaining to a sophomore, or to the second year of the college course; characteristic of sophomores: as, sophomore studies; sophomore rhetoric.

from the GNU version of the Collaborative International Dictionary of English.

• noun One belonging to the second of the four classes in an American college, or one next above a freshman.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective US The second in a series, especially, the second of an artist’s albums or the second of four years in a high school (tenth grade) or university.
• noun US A second-year undergraduate student in a college or university, or a second-year student in a four-year secondary school or high school.
• noun US (horse-racing) A three year old horse.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective used of the second year in United States high school or college
• noun a second-year undergraduate