A reverse split is the opposite of a split.

A 2:1 split means you get 2 shares for every 1 you own; cuts the pps in half.
Ex: 2:1 split on my 100 shares @ .10 gives me 200 shares @ .05


If it were a 1:2 reverse split, you would get 1 share for every 2 you own; doubles the pps.
Ex: 1:2 reverse split on my 100 shares @ .10 gives me 50 shares @ .20

http://www.investopedia.com/terms/r/reversesplit.asp