conformist
This term carries a strong social connotation, often implying a lack of individuality or a passive acceptance of the status quo. While it can be neutral in a descriptive sense, it is frequently used pejoratively to describe someone who lacks the courage to challenge authority or think independently. In religious contexts, the word specifically denotes adherence to a particular set of doctrines or an established church. This usage is more formal and less focused on the social pressure of "fitting in" than the general secular usage.
Meanings
A person who behaves according to accepted standards, rules, or traditional customs of a group or society.
"He was a lifelong conformist who never questioned the company's rigid dress code."
Following the established customs, rules, or styles of a particular group or society.
"The new architecture is surprisingly conformist, blending in perfectly with the surrounding colonial buildings."