Rashbam is a Hebrew acronym for רבי שמואל בן מאיר (Rabbi Shmuel son of Meir) (c.1085 - c.1158). His father was Meir ben Shmuel and his mother was Yocheved, the daughter of Rashi. Like his grandfather Rashi, the Rashbam was a biblical commentator and Talmudist. He was also a leading French Tosafist. He was the older brother of the Tosafist Rivam and the Tosafist Rabbeinu Tam, also known as Jacob ben Meir. Wikipedia
The definitive Wikipedia entry for Rashbam. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Rashbam