Disingenuous: lacking in frankness, candor or sincerity. Slightly dishonest or not speaking the complete truth.
If you leave an important fact out when trying to persuade someone to your theology, simply because they "didn't ask," this is disingenuous!
Understanding this when we as Christians reach out to nonbelievers, it is important to reveal all truths, good or bad and likewise, for the nonbelievers to do so as well.
This goes for an atheist, and any religion that is introducing new non biblical beliefs, especially doctrine.
Listen in to the My New Life Podcast and hear how damaging being disingenuous can be.