From the Greek for "image breaking", it was opposition to the use of Christian religious images in churches
.... Iconoclasm (Eikonoklasmos or 
, "Image-breaking -- - ") is the name of the heresy of 
opposition to the religious use of images and veneration of pictures and statues... [DOC] [TLE] Iconoclastic Controversy | Project Gutenberg Self-Publishing ... [PAR] The Western church remained firmly in support of the use of images ... 
Iconoclasm, Greek for "image-breaking", is the deliberate destruction within a 
culture of the ...