Lexical Definition

‎ἀκυρόω‎ akyróō (ak-oo-ro'-o) to nullify ^G:V
from ‎Α‎ (as a negative particle) and ‎κυρόω‎

disannul, make of none effect.

• to invalidate

Abbott-Smith

**† ἀκυρόω, -ῶ (< κῦρος, authority), [in LXX: I Es 6:32, IV Mac6*;]
to revoke, invalidate (MM, VGT, s.v.): Mt 15:6, Mk 7:13, Ga 3:17 (Plut.).†

Abbott-Smith References

Liddell-Scott-Jones

ἀκυρόω,

cancel, set aside, ψήφισμα, δόγμα, [Refs 4th c.BC+] (passive, [Refs 1st c.BC+]

__2 set at naught, treat as of no effect, [LXX+NT+1st c.AD+]
__2.b reject, deny the validity of, [Refs 1st c.BC+]
__3 metaphorically, render powerless, τῷ λογισμῷ τὸν τῶν παθῶν οἶστρον[LXX]

_{LSJ Scripture Refs: Matt.15.6}