Who is Nun in The Bible?

Yes.

If you're looking for the Word "nun" as we use it, you won't find it (Nun is mentioned as the name of Joshua's father in the Hebrew Bible, though). You also won't find the Words rapture, trinity, athiest, divinity, or incarnation. However, the ideas that all of these Words represent are clear in scripture.

The prophetess Anna lived as a cloistered nun (Luke 2:36-37). There was an order of widows living the consecrated life after the deaths of their husbands (1Tim. 5:3-12). Paul warned that women were not to be enrolled in this order if they had intentions of leaving the consecrated life to get married and so "incur condemnation for having violated their pledge" (1 Tim. 5:12).

The Nazirites ("consecrated ones"), were were essentially monks and nuns. They took vows of self-denial (Num. 6:2-4, 6-8) and had a distinctive appearance (Num. 6:5). John the Baptist was one of these "monks" (Luke 1:15), as were Samson (Judges 13:5-6) and Samuel (1 Sam. 1:11) . In the Christian age Paul took a temporary Nazirite vow (Acts 18:18) and recommended that others live celibate lives, consecrated to God (1 Cor. 7:32-38), especially ministers (1 Tim. 2:3-4).