Syme is an English dictionary for instant messaging services like GTalk and XMPP/Jabber.
It is quite simple to use: you add the following user to your contact list:
Then you send him a message with the word you are looking for and he will reply with its definition. For example, if you send the word ajar, Syme will reply:
adj 1: slightly open; "the door was ajar"
Syme can also search for synonyms. For doing that, just send him a message with the prefix "s:" and then the word; for example: s:ludicrous:
Synonyms of ludicrous:
ridiculous, preposterous, nonsensical, laughable, idiotic, derisory, cockeyed, absurd, ridiculous, farcical