The phrase "freezer door" refers to a door on a refrigerator or a separate freezer unit that you can open and close to access the frozen food inside. Full definition
Keep refrigerator and freezer doors closed as much as possible. (rismedia.com)
You just stand there staring in the pantry, opening and closing the refrigerator and freezer door waiting for something to jump out at you. (nutritiouseats.com)
I even looked for a replacement part, but they don't sell it (short of buying a new freezer door). (theinspiredroom.net)