look up any word, like bangarang:
 
1.
1. A term used to represent shaking your fist at someone via the internet
in the sense of an EMOTICON.

2. When using it as a plural (ie. shakeS fist) or as an ACTION, then the proper usage would be "shakes fist" as two SEPERATE words.
Examples:

1. :shakefist:

2. :shakes fist at (place name here):
by Grammar/Spelling Police September 21, 2005