Friberg Lexicon:
13974 ἰδιώτης, ου, ὁ strictly, one in private life layman or nonspecialist, with the specific sense taken from contrast in the context; (1) uneducated, unlearned (AC 4.13); (2) nonmember of a community, uninstructed person, inquirer (1C 14.16, 23, 24); (3) unskilled, untrained (2C 11.6)
Louw-Nida Lexicon:
27.26 ἰδιώτης, ου m: a person who has not acquired systemic information or expertise in some field of knowledge or activity - 'layman, ordinary person, amateur.' εἰ δὲ καὶ ἰδιώτης τῷ λόγῳ, ἀλλ᾽ οὐ τῇ γνῶσει 'perhaps I am an amateur in speaking, but certainly not in knowledge' 2 Cor 11.6.
In 1 Cor 14.16 ἰδιώτης is used to refer to a class of persons who were neither unbelievers nor fully instructed Christians, but who were inquirers or catechumens. In such a context, ἰδιώτης may be rendered as 'ordinary, uninitiated' επεὶ ἐὰν εὐλογῇς ἐν πνεύματι, ὁ ἀναπληρῶν τὸν τόπον τοῦ ἰδιώτου πῶς ἐρεῖ τὸ Ἀμήν ἐπὶ τῇ σῇ εὐχαριστίᾳ 'when you give thanks to God in spirit only, how can an ordinary, uninitiated person taking part in the meeting say ''Amen'' to your prayer of thanksgiving').
LS Greek Lexicon:
21162 ἰδιώτης
ἰδιώτης, ου, ὁ, (ἴδιος) a private person, an individual, ξυμφέροντα καὶ πόλεσι καὶ ἰδιώταις Thuc., etc.
II. one in a private station, opp. to one taking part in public affairs, Hdt., Att.; opp. to στρατηγός, a private soldier, Xen.
2. a common man, plebeian, Plut.
3. as Adj., ἰδ. βίος a private station, homely way of life, Plat.
III. one who has no professional knowledge, as we say 'a layman,' ἰατρὸς καὶ ἰδιώτης Thuc.; opp. to ποιητής, a prose-writer, Plat.; to a trained soldier, Thuc.; to a skilled workman, Plat.
2. c. gen. rei, unpractised, unskilled in a thing, Lat. expers, rudis, ἰατρικῆς Id.; also, ἰδ. κατά τι Xen.
3. generally, a raw hand, an ignorant, ill-informed man, Id., Dem.
IV. ἰδιῶται one's own countrymen, opp. to ξένοι, Ar. Hence ἰδιωτικός
VGNT Dictionary:
1972 ἰδιώτης [pg 299]
ἰδιώτης.
In Syll 84716 (Delphi—B.C. 185) the witnesses to a manumission are the priest, two representatives of the ἄρχοντες, and five ἰδιῶται, “private citizens”: cf. ib. 8468 (B.C. 197) and OGIS 9052 (B.C. 196) where again a distinction is drawn between ἱερεῖς and οἱ ἄλλοι ἰδιῶται. In connexion with the difficult 1 Cor 1416 ,23, Thieme (p. 32) cites Magn 9926 (beg. ii/B.C.) φερόμενον ὑπὸ τῶν @ἰ]διωτῶ@ν, where the word may have some reference to worship at the founding of a sanctuary in honour of Serapis, but the context is far from clear. In P Fay 1912 (ii/A.D.) the Emperor Hadrian refers to his father’s having died at the age of forty—ἰδιώτης, “a private person,” and in P Oxy XII. 140914 (A.D. 278) we read of overseers chosen—ἐξ ἀρχόντων ἢ καὶ ἰδιωτῶν, “from magistrates or private persons”: cf. P Ryl II. III (a)17 (censusreturn—c. A.D. 161) ἰδιώ(της) λαογ(ραφούμενος), “a private person paying polltax.” The adj. ἰδιωτικός is similarly used with reference to a private bank—ἰδιωτικὴ τράπεζα—in P Lond 116821 (A.D. 18) (= III. p. 137), and in ib. 9328 (A.D. 211) (=III. p. 149) with reference to δάνεια ἤτοι ἰδιωτικὰ ἢ ὃημόσια: cf. the Will, P Tebt II. 38118 (A.D. 123) (= Selections, p. 79), where Thaesis bequeaths her property to her daughter on condition that she discharges, her private debts—διευλυτώσει ὧν ἐὰν φανῆι ἡ Θαῆσις ὀφίλουσα ἰδιοτικῶν χρεῶν, and BGU V. 121O196 (c.A.D. 150) Παστοφόρo@ις] evξὸν ἰδιωtikw|u evφίεσθαι τάξεων, “Pastophoren ist es erlaubt, nach Laienstellungen zu streben” (Ed.). See further Preisigke Fackwörter, p. 1011. To the rare use of ἰδιώτης to denote absence of military rank, a private, in P Hib I. 3021 (B.C. 300–271) and ib. 897 (B.C. 239), we can now add P Harnb I.2611 (B.C. 215). In contrast to rhetoricians and philosophers, Epictetus describes himself as ἰδιώτης (iii. 7. 1, al.): cf. 2 Cor 116, and see Epict. iii. 9. 14 οὐδὲν ἦν ὁ Ἐπίκτητος, ἐσολοίκιζεν, ἐβαρβάριζεν (cited by Heinrici Litt. Char. p. 2).
Edit: Changed 'Scriptures' for things of the Spirit