Kill a process by name with pkill:
$ ps -A | grep "ruby"
12264 ttys002 0:03.57 ruby guard
12288 ttys002 0:05.61 ruby spork -p 8989
12289 ttys002 0:05.78 ruby spork cu -p 8990
95903 ttys002 0:03.64 ruby yard server -p 8808
13364 ttys007 0:00.00 grep ruby
$ pkill -9 -f ruby
$ ps -A | grep "ruby"
13835 ttys007 0:00.00 grep ruby
-f will match against all arguments, instead of just the process name.