Dictionaries can be changed. That much is only a function of language.
then be honest - you want to redefine marriage.
There's a long tradition of redefining marriage, starting from the creation of civil marriage, the change in women's status from property to equal partner, changing views on divorce, the allowance of interfaith marriages, development of marriage for love, development of marriage for seniors, and the legalization of interracial marriage. Within the current definition of marriage, allowing same-sex unions to be counted is not as dramatic as other changes.