We wouldn't call it a full dictionary but WordRoll EF can be your handiest and quickest English/French reference in your pocket. It provides direct and precise word to word translations between English and French.
Plus, everything is on one page, probably the longest page you will ever see. The page scrolls as you type right into the entry you look for. No selecting, no navigating, the content is there the moment you complete typing.
iPhone OS 2.x