brush up

Verb

brush up (third-person singular simple present brushes up, present participle brushing up, simple past and past participle brushed up)

1. To paint, or make clean or bright with a brush.
   • April 10, 1706, Alexander Pope, letter to William Wycherley
     You have commissioned me to paint your shop, and I have done my best to brush you up like your neighbours.
2. (idiomatic) To review; to improve an existing but rusty or underdeveloped skill.
   • I'll need to brush up (on) my Greek before my trip to Athens.
   • How many will be rich enough to travel in style is difficult to know—but already 30% of the guests at the very expensive Mandarin Oriental in Hong Kong are from mainland China. Reception staff around the world had better start brushing up their Mandarin language skills.2010 December 7, J.A., “Travel in style”, in The Economist

   Synonyms:

   rub up

3. (slang, transitive) To beat up, annoy or insult (someone).