Source : Webster's Revised Unabridged Dictionary (1913)

Crammer \Cram"mer\ (kr[a^]m"m[~e]r), n.
   One who crams; esp., one who prepares a pupil hastily for an
   examination, or a pupil who is thus prepared. --Dickens.

Source : WordNet®

crammer
     n 1: a student who crams
     2: a teacher who is paid to cram students for examinations
     3: a special school where students are crammed
     4: a textbook designed for cramming