\Ra"ca\, a. [Gr. ?, from Chaldee r[=e]k[=a].] A term of reproach used by the Jews of our Savior's time, meaning ``worthless.'' Whosoever shall say to his brother, Raca, shall be in danger of the council. --Matt. v. 22.
vain, empty, worthless, only found in Matt. 5:22. The Jews used it as a word of contempt. It is derived from a root meaning "to spit."
Webster's 1913 Dictionary