Currently, the options available are:
Commandline options (privmsg $botnick or typed in channel):
To look up a word, simply use : .dict <word>
To show only the word origin : .dict dcorigin <word>
To show only synonyms/antonyms: .dict dcsyn <word>
Script Configure Options:
# Channels where we allow public use
set dcomchans "#mychan #chan2 #etc"
# Channels that only respond via privmsg
set dcquietchans "#chan2 #etc"
# Timeout for geturl
set dcomtimeout "30000"
# If you want limit output, set the line-limit here
#(this will truncate results.) Set to 0 for no-limit.
set dclinelimit 0
# Show Word Origins when available? 1 == yes, 0 == no
set dcorigin 1
# Show Synonyms and Antynoms for words? 1 == yes, 0 == no
set dcsynant 1
Dictionary.com provides the following additional databases, which will be incorporated into this script:
American Heritage Dictionary
Webster's 1913 Dictionary
WordNet v2.0
American Heritage Steadman Medical Dictionary
Merriam Webster Medical Dictionary
Free On-line Dictionary of Computing (FOLDOC)
Internet Jargon File
Wallstreet Words
Investopedia
Merriam-Webster's Dictionary of Law
I'd appreciate people testing the script and sending me words that produce errors (showing html codes or truncated results for example. Dictionary.com tends to use a LOT of unicode chars and short of adding thousands of them to the string map, I've been adding them as I see them.)
Keep in mind this is a preview of the script, the other databases are not yet incorporated, although the regexp's are in place (just need to finish them to format the results

Check the url for updates, there will no doubt be many

http://members.dandy.net/~fbn/dictcom.tcl.txt