referring to to proclaim one's actions or words as coming from the Judaeo-Christian God when in fact the actions or words are not from God at all. Reference Exodus verse similar to "You shall not make wrongful use of the name of your God".
This commandment has nothing to do with the phrase "God dammit" as many superstitious simpletons have comes to believe.
Examples of taking the Lord's name in vein are:
"God told me that you should let me marry your 13 year old daughter"
"In the name of Jesus, I command you to . . "
"God sent me to do this"
"I am on a mission from God"
"God told me to tell you to send in 1 million dollars, operators are standing by."
"God hates fags"
"God hates America"
"God caused natural disaster A, B, C to punish group A, B, C"
"God told me blah blah blah"