Many Palm users are familiar with the free dictionary, Noah Lite. Noah Lite has 30,000 words, but no pronunciation guide or example sentences. Noah Lite was the free version to interest you in the $20 Noah Pro. Noah Pro has definitions of 122,000 words, a colorful display, examples, synonyms, and more. Unlike Noah Lite, you can run Noah Pro from an expansion card, which is helpful since it is 5MB in size. Unfortunately, ArsLexis is no longer in business and Noah Lite is no longer available. However, they have made the full version of Noah Pro available for free! Download it here.
Noah Pro has a "Resident mode" where you can highlight a word in another application, do the command bar stroke in Graffiti, and tap the N icon in the bar. Noah Lite then launches and looks up that word. Unfortunately, I could not get this function to work properly on my Palm TX. I did, however, set Noah Pro's Startup Action preference to "clipboard" so that whenever I launch Noah Pro, it displays the word that I last copied. Pretty handy if you ask me!
In addition, ArsLexis offered a thesaurus with 48,000 words. Thesaurus is now available for free as well! It will take up about 400k of memory, either on a card or in your Palm handheld's main memory.
Noah Pro and Thesaurus come with detailed documentation so you can explore all of the features they have to offer. Be aware, that just like many complete dictionaries, words that you would never want to hear come out of children's mouths are clearly defined in Noah Pro and Thesaurus.
Pocket PC users, don't forget you can download the free Encarta Pocket Dictionary. iPod users don't have a free dictionary offering, but for $10, you can have the Merriam-Webster's Pocket Dictionary on your 'pod.