It’s an adjective and it means not having or lacking enthusiasm. If someone is unenthusiastic about something it means they are feeling indifferent, apathetic, passive, phlegmatic, lukewarm, listless, languid, lethargic, emotionless, perfunctory about it.
lacking giving a shit, such as the difference between taking home your ex and taking home a new girl. Can also be used in many situations involving boredom and mundane activities.
You seem a little unthusiastic about helping me clean out my basement.
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".