Exec and Top brass

Exec noun - A person who manages or directs something.

Top brass and exec are semantically related In some cases you can use "Top brass" instead a noun "Exec".

Top brass noun - The most important persons in a governing body.

Exec and top brass are semantically related in expert topic. You can use "Exec" instead a noun phrase "Top brass", if it concerns topics such as person representing organization, person who manages an organization, leader of military or other organization.