what’s another word for a multi tasker?

I don’t know if “multi tasker is even officially a word, but it’s the only word I can think of that’s synonymous with the word I’m trying to find. I found it in the dictionary yesterday and I can remember the definition, but not the word. It’s driving me nuts because I wanted to use it against my boss. He claims he has to do everything, whereas I actually do everything. The definition went like this; ” an employee who has many duties”. Please help, it’s giving me a head ache trying to remember this word.