backdoor vs back door

backdoor and back door both are nouns.

Word	Noun	Adjective	Verb	Adverb
backdoor	Yes	No	No	No
back door	Yes	No	No	No

As nouns, backdoor and back door are synonyms defined as:

backdoor and back door: a secret or underhand means of access (to a place or a position)

As nouns, backdoor and back door are synonyms defined as:

Other synonyms of backdoor include back entrance.

As nouns, backdoor and back door are synonyms defined as:

backdoor and back door: an undocumented way to get access to a computer system or the data it contains

backdoor (noun)	back door (noun)
a secret or underhand means of access (to a place or a position)	a secret or underhand means of access (to a place or a position)
an entrance at the rear of a building	an entrance at the rear of a building
an undocumented way to get access to a computer system or the data it contains	an undocumented way to get access to a computer system or the data it contains