Apparently a primary word; foreign (literally, alien, or figuratively, novel); by implication, a guest or (vice-versa) entertainer -- host, strange(-r).
1. a foreigner, stranger (opposed to ἐπιχώριος, Plato, Phaedo c. 2, p. 59 b.; Josephus, b. j. 5, 1, 3);
a. properly: Matthew 25:35, 38, 43; Matthew 27:7; 3 John 1:5; ξένοι καί παρεπίδημοί ἐπί τῆς γῆς, Hebrews 11:13; οἱ ἐπιδημοῦντες ξένοι, Acts 17:21; opposed to συμπολίτης, Ephesians 2:19; (the Sept. for אֹרֵחַ, a traveler, 2 Samuel 12:4, Alex. manuscript; for נֵר, Job 31:32; several times for נָכְרִי). (as adjective with) δαιμόνια, Acts 17:18.
b. tropically, α. alien (from a person or thing); without knowledge of, without a share in: with a genitive of the thing, τῶν διαθηκῶν τῆς ἐπαγγελίας, Ephesians 2:12 (cf. Winer's Grammar, § 30, 4, 6) (τοῦ λόγου, Sophocles O. T. 219). β. new, unheard of: διδαχαι, Hebrews 13:9; ξένον τί a strange, wonderful thing, 1 Peter 4:12 (Aeschylus Prom. 688; Diodorus 3, 15 and 52; others).
2. one echo receives and entertains another hospitably; with whom he stays or lodges, a host: ὁ ξένος μου, Romans 16:23, where καί τῆς ἐκκλησίας ὅλης is added, i. e. either 'who receives hospitably all the members of the church who cross his threshold,' or 'who kindly permits the church to worship in his house' (Fritzsche).