Nolo has developed a free legal dictionary for the iPhone. Nolo's Plain English Law Dictionary "contains nearly 4000 legal terms defined in everyday, understandable language," according to the iTunes descriptions.
Here's more about the app from iTunes:
"You'll find both the legal standards--Latin terms, courtroom jargon, contract basics--and newly minted terms that reflect the ever changing language of the law today. What does it mean to get "dooced"? Do you need that "pre-dup"? Had a run-in with a "patent troll" lately? Nolo is committed to finding and defining the latest twists in legal language that have entered our daily conversations--important words not found in other legal dictionaries. Nolo's Plain-English Law Dictionary is both authoritative and friendly, but it is not your grandfather's law dictionary."
Hat tip to WisBlawg.