What is "to brush up"

Brush \Brush\, v. t. [imp. & p. p. Brushed (br[u^]sht); p. pr. & vb. n. Brushing.] [OE. bruschen; cf. F. brosser. See Brush, n.]

1. To apply a brush to, according to its particular use; to rub, smooth, clean, paint, etc., with a brush. ``A' brushes his hat o' mornings.''
   --Shak.

2. To touch in passing, or to pass lightly over, as with a brush.

   Some spread their sailes, some with strong oars sweep The waters smooth, and brush the buxom wave.
   --Fairfax.

   Brushed with the kiss of rustling wings.
   --Milton.

3. To remove or gather by brushing, or by an act like that of brushing, or by passing lightly over, as wind; -- commonly with off.

   As wicked dew as e'er my mother brushed With raven's feather from unwholesome fen.
   --Shak.

   And from the boughts brush off the evil dew.
   --Milton.

   To brush aside, to remove from one's way, as with a brush.

   To brush away, to remove, as with a brush or brushing motion.

   To brush up, to paint, or make clean or bright with a brush; to cleanse or improve; to renew.

   You have commissioned me to paint your shop, and I have done my best to brush you up like your neighbors.
   --Pope.