Strong's G3154 · Greek

ματαιόομαι

mataioo · mat-ah-yo'-o

from 3152; to render (passively, become) foolish, i.e. (morally) wicked or (specially), idolatrous

Scholarly Lexicons

Abbott-Smith Manual Greek Lexicon

 1 † ματαιόω , -ῶ ( μάταιος ), [in LXX: IV Ki 17:15 , Je 2:5 , al. הבל , etc.;] to make vain , foolish : Ro 1:21 .† 

G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain