Terminology 3 is the latest version of Agile Tortoise's dictionary and thesaurus app. Terminology is a great way to look up words or find replacements. You can drill down, finding more and less specific words from your current search. You can find related words, research parts of certain words and more. Search is accessed either by hitting the magnifying glass on the bottom toolbar or by swiping right from the left edge of the screen.
Like Agile Tortoise's Drafts, Terminology 3 supports actions, which let you do things like search Wikipedia for your current word, or execute a custom action. For instance, I have an action in Terminology that allows me to send words to a specific Evernote notebook. Access actions by tapping the button in the bottom right corner of the screen. From the sliding panel, you can choose your actions, as well as visit the action directory. Manage your actions by hitting the gear icon to go to settings, then tap Manage Actions.
Terminology allows you to customize the app's appearance with several fonts and color schemes. Additionally, you can choose to sync you favorite terms, custom actions, and history with iCloud, in addition to Dropbox. Terminology 3 is a new app, requires iOS 7, and is now universal. You can grab it from the App Store for $2.99.
If you try it, let me know how it works for you!