Lesboy would be a cusper lesbian, cross-aligned (guy-aligned/solarian gal or girl-aligned/lunarian boy), multigender/polygender (girlboy/boygirl), sapphogender/lesbogender guy or otherwise a boy that is gay for women.
Similar to saphboy/saphguy, gyneurnimasculine (lesboi/saphboi), boydyke/guydyke and lesbutch. Just as these terms don’t mean necessarily “lesbian man” or “male lesbian”, lesboys aren’t all men, they can be pleonotic boys.