How about if I just give you what the lexicon says ...
"Strong’s Definitions
ψυχικός psychikós, psoo-khee-kos'; from
G5590; sensitive, i.e. animate (in distinction on the one hand from
G4152, which is the higher or renovated nature; and on the other from
G5446, which is the lower or bestial nature):—natural, sensual."
"Outline of Biblical Usage
- of or belonging to breath
- having the nature and characteristics of the breath
- the principal of animal life, which men have in common with the brutes
- governed by breath
- the sensuous nature with its subjection to appetite and passion"
"Thayer's Greek Lexicon
STRONGS NT 5591: ψυχικός
ψυχικός, ψυχική, ψυχικόν (ψυχή) (Vulg.animalis, Gem.sinnlich), "of or belonging to the ψυχή;
a. having the nature and characteristics of the ψυχή i. e. of the principle of animal life," which men have in common with the brutes (see ψυχή, 1 a.); (A. V. natural): σῶμα ψυχικόν,
1 Corinthians 15:44; substantively, τό ψυχικόν(Winer's Grammar, 592 (551)),
1 Corinthians 15:46: since both these expressions do not differ in substance or conception from σάρξ καί αἷμα in
1 Corinthians 15:50, Paul might have also written σαρκικον; but prompted by the phrase ψυχή ζῶσα in
1 Corinthians 15:45 (borrowed from
Genesis 2:7), he wrote ψυχικόν.
b. "governed by the ψυχή i. e. the sensuous nature with its subjection to appetite and passion (as though made up of nothing but ψυχή): ἄνθρωπος (equivalent to σαρκικός (or σάρκινος, which see 3) in
Genesis 3:1),
1 Corinthians 2:14; ψυχικοί, πνεῦμα μή ἔχοντες,
Jude 1:19 (A. V. sensual (R. V. with marginal reading 'Or natural, Or animal'); so in the following example); σοφία, a wisdom in harmony with the corrupt desires and affections, and springing from them (see σοφία, a., p. 581b bottom),
James 3:15. (In various other senses in secular authors from Aristotle and Polybiusdown.)"
Hence, the "natural" man can be defined as the physical man.