Reference: Raca
American
A word derived from a Hebrew word signifying vain, trifling, brainless; otherwise, beggarly, worthless. It is thus translated by the Vulgate, in Jg 11:3; in the English, "vain men." The word includes a strong idea of contempt. Christ says, Mt 5:22, whoever shall say to his brother, "Raca," shall be condemned by the council, or sanhedrim. The term translated "fool" in the same passage, means vile and abandoned wretch.
Easton
vain, empty, worthless, only found in Mt 5:22. The Jews used it as a word of contempt. It is derived from a root meaning "to spit."
Fausets
Hastings
A term occurring only in Mt 5:22. It is a Semitic word, probably a popular pronunciation of the Rabbinic r
Morish
An Aramaic word signifying 'worthless,' a term of great contempt. Mt 5:22.
Smith
Raca,
a term of reproach derived from the Chaldee reka, worthless. ("Raca denotes a certain looseness of life and manners, while 'fool,' in the same passage, means a downright wicked and reprobate person.")
Watsons
RACA, a Syriac word which properly signifies empty, vain, beggarly, foolish, and which includes in it a strong idea of contempt. Our Saviour pronounces a censure on every person using this term to his neighbour, Mt 5:22, Lightfoot assures us that, in the writings of the Jews, the word raca is a term of the utmost contempt, and that it was usual to pronounce it with marked signs of indignation.