Blasphemy is speaking evil of God or denying Him some good which we should attribute to Him. It could also be understood to be acting in any impious, mocking or contemptuous way toward any member of the Trinity.1 The word blasphemy comes from the Greek word , blasphemia, meaning "curse" or "vilifying."2 Blasphemy arises out of pride (Psalm 73:9,11), hatred (Psalm 74:18), injustice (Isaiah 52:5), etc. Christ was often mistakenly accused of blasphemy by Jewish leaders (John 10:30-33).
"In the OT the penalty for blasphemy against God is death by stoning (Lev. 24:16; cf. Jn. 10:33; Acts 6f [Stephen]). According to 1 S. 3:13, Eli’s sons blasphemed God (RSV and NEB, following LXX; the AV has “made themselves vile,” following MT). In Neh. 9:18, 26, Ezra refers to the “great blasphemies” of the Israelites of old. And Ezk. 20:27ff. speaks of the blasphemy of ancient Israel in sacrificing on the high places." (Bromiley, Geoffrey W., ed. The International Standard Bible Encyclopedia, Revised. Wm. B. Eerdmans, 1979–1988.)