2. Belonging to, characteristic of, or constituting another and very different place, society, or person; strange. See Synonyms at foreign. 3. Dissimilar, inconsistent, or opposed, as in nature: emotions alien to her temperament.
n, pl -thens or -then. 1. (Alternative Belief Systems) a person who does not acknowledge the God of Christianity, Judaism, or Islam; pagan. 2. an uncivilized or barbaric person. 3. (Alternative Belief Systems) the heathen (functioning as plural) heathens collectively.
The definition of libertine is someone who has a lack of morality, or someone who rejects customary religious beliefs and thinks freely. Promiscuous behavior and sleeping around are an example of something that would be described as libertine actions.