From Paragon Technologie:
This explanatory dictionary of American and British English contains 140,489 entries (5500 Kb of RAM). Dictionary is based on WordNet lexical database by the Cognitive Science Laboratory at Princeton University. It is based on SlovoEd dictionary engine for all devices with Palm OS 3.1 and higher. It has convenient interface and unique data compression technology. Dictionary runs fast and effectively despite the high data compression ratio. The program also includes a resident module that allows you to search words without switching between applications.
Dictionary has user friendly, intuitive understandable interface with many easy-to-use unique features:
Resident module that allows you to look for the explanations of words from within the currently active application (except Handspring Treo devices with hardware keyboard).
Full screen and standard modes to show the word explanation.
The possibility to add new entries, remove and edit existing entries using powerful built-in editor.
The possibility to activate/deactivate all changes of entries and synchronize changes with desktop computer.
Complete selection functionality - you can select any words from translation field!
A number of user defined preferences that make the program very flexible (for example, changable font size in translation field - in order to see more entries).
Availability to install several dictionaries at the same time (you can have the English-English dictionary installed together with translation dictionaries, for example, English-Spanish).
High-quality dictionary databases specially adapted for using on Palm OS based devices.
Possibility to install to expansion cards (Memory Stick, Compact Flash, Secure Digital, MMC).