Lexical Definition

‎ἀσύνθετος‎ asýnthetos (as-oon'-thet-os) untrustworthy ^G:A
from ‎Α‎ (as a negative particle) and a derivative of ‎συντίθεμαι‎

covenant-breaker.

• properly, not agreed, i.e. treacherous to compacts

Abbott-Smith

ἀ-σύν-θετος, -ον (< συντίθεμαι; v. M, Pr., 222; MM, s.v.), [in LXX: Je 3:7, 8, 10, 11 (בּגד)*;]
false to engagements, not keeping covenant, faithless (MM, s.v.): Ro 1:31.†

Abbott-Smith References

Liddell-Scott-Jones

ἀσύνθετος-θετος, ον,

(συντίθημι) uncompounded, [Refs 5th c.BC+]; ἀ. φωνή a word standing alone, [Refs 3rd c.BC+]. adverb -τως[Refs]

__II (συντίθεμαι) bound by no covenant, faithless, ὁ δῆμός ἐστιν πρᾶγμα τῶν πάντων ἀσυνθετώτατον[NT+4th c.BC+]; making no covenants, ἀ. διατελοῦσι[Refs 1st c.BC+]

_{LSJ Scripture Refs: Rom.1.31}