Definitions

1. noun

a term of endearment or a colloquial expression for a friend or companion, especially a male one

“Come on, bucko, let’s get some lunch.”

2. noun

a colloquial term for a person, especially a sailor, who is considered to be in charge or responsible

“The bucko of the ship’s crew was tasked with assigning duties to the other sailors.”

3. interjection

expressing agreement or confirmation, similar to ‘okay’ or ‘agreed’

“Bucko, I think you’re right.”