Backdoor rhymes with:
amador, bedore, commodore, ecuador, el-salvador, humidor, indoor, isidore, labrador, matador, oradour, outdoor, parador, salvador, san-salvador, stevedore, theodore, troubadour
Backdoor sounds like:
babysitter, backwater, bacteria, basketry, bastyr, baxter, bester, bigotry, bistro, bookstore, booster, boster, bostra, boughter, buchter, buster, bustier