Busy person and Spark plug

Spark plug and busy person are semantically related. in go-getter topic. In some cases you can use "Spark plug" instead a noun phrase "Busy person", when it comes to topics like eager beaver, industrious person.

Spark plug noun - Electrical device that fits into the cylinder head of an internal-combustion engine and ignites the gas by means of an electric spark.

Busy person and spark plug are semantically related. You can use "Busy person" instead a noun phrase "Spark plug".