the regular alternation of two distinct body forms in the life cycle of a plant or animal, usually an alternation between a form that reproduces sexually and one that reproduces asexually
See alternation of generations in American Heritage Dictionary 4
noun
The regular alternation of forms or of mode of reproduction in the life cycle of an organism, such as the alternation between diploid and haploid phases, or between sexual and asexual reproductive cycles. Also called metagenesis, xenogenesis.