Easton's Bible Dictionary (1897)
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.”
Smith's Bible Dictionary (1863)
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.”) (Matthew 5:22)
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
RA'CA (worthless), a term of contempt. Matt 5:22.
Hitchcock's Bible Names (1869)
worthless; good-for-nothing