1.AdjectiveThe 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.
"The band’s sophomore album built upon the success of their debut release, catapulting them to megastardom."
2.AdjectiveSophomoric.
3.NounA second-year undergraduate student in a college or university, or a second-year student in a four-year secondary school or high school.
"She was very mature for a sophomore and had several friends who were juniors or even seniors."
4.NounA three-year-old horse.
"The filly had looked promising as a sophomore, but concerns over her health had prompted the owner to pull her from the season’s early races."