Answer: boneup

AnswerCrossword Clue
BONEUP

Cram for an exam

BONEUP

Study hard

BONEUP

Cram for exams

BONEUP
Cram
BONEUP
Get ready for a test
BONEUPPrepare for, as a test
BONEUPStudy
BONEUPPrepare for an exam: Slang.
BONEUPStudy hard: Slang.
BONEUPStudy for exams: Slang.
BONEUPCram for an exam.
BONEUPTake a refresher course