Mug up on
Definition 1 of 1
Pro Tip 1/3Last-Minute Study
Used when studying a lot of information in a short time before an exam or meeting. 
I have to mug up on French verbs tonight for tomorrow's test.
Pro Tip 2/3Intensive Learning
Implies focused and concentrated study to understand a subject quickly. 
She's mugging up on her chemistry because she wants to ace the quiz.
Pro Tip 3/3Not Casual Reading
Indicates active learning, not just reading for pleasure or general interest. 
John isn't just reading; he's mugging up on Roman history for his dissertation.