LOST

[lawst]

noun:
-any person or persons who are not Christians
-any person or persons who have not prayed the sinner's prayer

adjective:
-preferred term used to describe non-Christians.

Let's use it in a sentence!
n: We really need to pray for the lost.
adj: Did you know that Jerry's parents are lost? He's the only Christian in his family.

Secular Synonyms:
Non-Christian, Atheist, Agnostic, Buddhist, Muslim, Jew, Hindu, Mormon, Jehovah's Witness, Unitarian
Find it in the Bible:
Mt 18:11; Lk 15:24; 19:10; 2 Cor 2:3-4

Fun fact:
If you accidentally use this term in reference to the hit TV series, don't worry. Most young Evangelicals will know what you are talking about. However, doing so may lead them to express a lengthy lament about the the implied Universalist themes of the series finale and how it ruined the whole show.