As nouns the difference between crewmate and impostor
is that crewmate is a member of the same crew while impostor is someone who attempts to deceive by using an assumed name or identity.
impostor
Alternative forms
* imposter
* impostour (obsolete)
Noun
(
en noun)
Someone who attempts to deceive by using an assumed name or identity.
*
Synonyms
* impersonator
* See also