Lexical Definition

‎εἰκῆ‎ eikē (i-kay') in vain ^G:ADV
probably from ‎εἴκω‎ (through the idea of failure)

without a cause, (in) vain(-ly).

• idly, i.e. without reason (or effect)

Abbott-Smith

εἰκῇ (-ῆ, Rec., as in cl.), adv., [in LXX: Pr 28:25 (εἰκῇ)* ;]

1. without cause or reason: Mt 5:22 (E, mg.), Col 2:18 (ICC).
2. vainly, fruitlessly, to no purpose: Ro 13:4, I Co 15:2, Ga 3:4 4:11, Col 2:18.†

Abbott-Smith References

Liddell-Scott-Jones

εἰκῇ,

without plan or purpose, at random, at a venture, [Refs 6th c.BC+]

__II in vain, [NT+1st c.BC+]
__III slightly, moderately, ἀγγεῖα εἰ. πεπυρωμένα [Refs 2nd c.BC+]

_{LSJ Scripture Refs: 1Cor.15.2}