If someone blasphemes, they say rude or disrespectful things about God or religion, or they use God's name as a swear word. `Don't blaspheme,' my mother said The spiritual leader charged that the book blasphemed against Islam. + blasphemer blasphemers blas·phem·er Such a figure is liable to be attacked as a blasphemer. to speak in a way that insults God or people's religious beliefs, or to use the names of God and holy things when swearing (blasphemare, from , from blasphemos )