The client downloads the current word list from this URL: http://static.iminlikewithyou.com/drawsomething/wordlist.csv
I've been meaning to see if I can run a proxy and substitute my own words.
EDIT: I personally use wordplay (http://hsvmovies.com/static_subpages/personal_orig/wordplay/...) with the -lx flags on this file when I'm stumped