A workaholic is someone who works far too much and cannot easily stop — not just a busy person, but someone whose working has taken over the rest of their life. The key idea is that it is a habit they cannot control: a workaholic checks email in bed, takes the laptop on holiday, feels uncomfortable doing nothing. It is a noun (he's a workaholic) and can be used before another noun too (a workaholic father). The feeling of the word depends a lot on who says it. Spoken about yourself, it is often half a boast — "I'm a bit of a workaholic" can mean "I am dedicated." Spoken by a family member, it is a complaint: it usually means the person is not there for the people at home. In careful writing about health, it is closer to a real problem, near words like burnout and addiction. It is informal, and very common in everyday talk, in Taiwan too. Note that it says nothing about being good at the job — a workaholic may be excellent or simply unable to let go.