Definition of amitosis. : cell division by simple cleavage of the nucleus and division of the cytoplasm without spindle formation or appearance of chromosomes.
On the other hand, amitosis is a simple method of cell division (also called direct cell division) which occurs without formation of spindle fibres and appearance of chromosomes (by 'appearance of chromosomes', what I mean to say is that, the chromatin network, which is initially present in the form of long threads does not condense to form distinct structures called chromosomes.
In amitosis, the nuclear membrane remains intact, whereas karyokinesis (division of nucleus : karyo =nucleus, kinesis =division)takes place in mitosis.