Definition of gametophyte
:the haploid multicellular individual or generation of a plant or alga with alternation of generations that begins with a haploid spore, produces gametes by mitotic division, and ends with fertilization producing a diploid zygote and that constitutes the visibly dominant form in mosses and algae, exists as an independent plant body in ferns and their relatives, and is reduced to a microscopic or rudimentary state in seed plants — compare sporophyte
