LSJ
Hebr. word expressive of contempt, Ev. Matt. 5.22.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
TBESG
ῥακά (T, ῥαχά),
usually taken to represent the Aram. רֵיקָא, a shortened form of H7386, ' empty,' as vocalized in the Galilæan dialect; an expression of contempt, raca: Mat.5:22 (cf. DB, iv, 191 f.; and for other explanations, see Zorell, see word).†
(AS)
Translators Brief lexicon of Extended Strongs for Greek based on Abbot-Smith, A Manual Greek Lexicon of the New Testament (1922) (=AS), with corrections and adapted by Tyndale Scholars