noun.
One of two divisions of 15 to 18 weeks each of an academic year.
The Century Dictionary and Cyclopedia
noun.
A period or term of six months; specifically, one of the half-year courses in German and many other Continental universities, and hence in some colleges in the United States: as, the summer and winter semesters.
the GNU version of the Collaborative International Dictionary of English
noun.
A period of six months; especially, a term in a college or university which divides the year into two terms.