The Collaborative International Dictionary
Unchristian \Un*chris"tian\, a. [Pref. un- not + Christian.]
Not Christian; not converted to the Christian faith; infidel.
Contrary to Christianity; not like or becoming a Christian; as, unchristian conduct.
Unchristian \Un*chris"tian\, v. t. [1st pref. un- + Christian.]
To make unchristian. [Obs.]
--South.
Douglas Harper's Etymology Dictionary
1550s, "not professing Christianity" (of persons), from un- (1) "not" + Christian (adj.). Meaning "at variance with Christian principles" (of actions) is recorded from 1580s.
Wiktionary
a. 1 Not of the Christian faith. 2 Not in accord with Christian principles; without Christian spirit, unbefitting a Christian.
WordNet
adj. not of a Christian faith [ant: christian]
Usage examples of "unchristian".
She was sure it was very unchristian, and unfeminine to hate anyone this way, and yet she felt it with a depth and Tightness she could not deny.
Rome, towards sheer materialism, or towards an unchristian and unphilosophic spiritualism.
It were a most Unchristian and uncivil, yea a most unreasonable thing to imagine that the Fitt's of the Young Woman were but meer Impostures: And I believe scarce any, but People of a particular Dirtiness, will harbour such an Uncharitable Censure.
Of all the blackguardly, unchristian notions, storming in on wounded men and beasts—” Keynes was literally shaking his fist in Barham’s face.
Of all the unchristian beverages that ever passed my lips, Turkish coffee is the worst.