Which word can be used to describe a self-important attitude?

The term "conceit" is accurately used to describe a self-important attitude. Conceit refers to an excessive appreciation of one's own worth or abilities, often manifesting as arrogance or vanity. When someone exhibits conceit, they typically view themselves as superior to others, which creates a self-important demeanor.

In contrast, the other terms do not convey this meaning. "Concord" refers to a state of agreement or harmony between people or groups. "Conjoin" means to join together or unite, without the connotations of self-importance. "Concur" implies agreement or having the same opinion as someone else, which also lacks any implication of self-importance. Therefore, "conceit" is the most fitting term for describing a self-important attitude.