Boyd’s Bible Dictionary:
(injurious speaking). Speaking evil of God (Lev. 24:11; Psa. 74:18; Isa. 52:5; Matt. 12:32; Acts 18:6; Rom. 2:24; Col. 3:8). Royalty could be blasphemed (1 Kings 21:10). Punished by stoning (Lev. 24:11-14).
Concise Bible Dictionary:
In scripture this does not always refer to speaking evil of God, to which the word is now restricted. The same Greek word is translated “railing” in 1 Timothy 6:4 and Jude 9; and “evil speaking” in Ephesians 4:31, as it might well be rendered elsewhere. Blaspheming the name of the Lord was under the Jewish economy punishable by death: the son of Shelomith who had married an Egyptian, was stoned to death for this sin (Lev. 24:11,14,23). The blasphemy against the Holy Ghost was attributing the Lord’s action of casting out demons to the agency of Satan—a sin which should not be forgiven in this age nor in the age to come. The context shows that “the unpardonable sin” refers to this particular form of blasphemy (Matt. 12:24-32).
Strong’s Dictionary of Hebrew Words:
Meaning:
or nematsah {neh-aw-tsaw'}; from 5006; scorn