WordNet (r) 3.0 (2006):

refresher course
    n 1: a course that reviews and updates a topic for those who
         have not kept abreast of developments [syn: refresher
         course, refresher]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "refresher course":
   academic specialty, area, classical education, core curriculum,
   course, course of study, curriculum, discipline, elective, field,
   general education, general studies, humanities, liberal arts,
   major, minor, proseminar, quadrivium, scientific education,
   seminar, specialty, study, subdiscipline, subject,
   technical education, trivium