What is adjective form of “initiative”?

Question

Merriam-Webster says "initiative" can be also an adjective, however, it is adjectival from "to initiate", meaning "introductory" or "preliminary". What is then the correct adjective of "initiative" as in "this guys shows great initiative"? This guy is...?

Edit: I am afraid I did not phrase my question clearly: I am not interested in the meanings derived from "to initiate", actually I was quite surprised to find out this other meaning of the word. My question relates to -- what I believe is today's prime meaning of the word -- initiative as a positive quality in people who come up with their own solutions, need not to be told exactly what to do, etc. These people are ...?

Answer 1

Somewhat to my chagrin, I think I'd go with proactive.

The adjective usage of initiative that you're finding documented would have to be spoken as "inish-ee-aytiv" (as opposed to the noun "inish-uh-tiv") in order to be understood, it would sound distractingly odd, and your chances of getting your meaning across still aren't too hot. In written communication it would be a total loss.

In some circumstances you could go with a fairly close mapping to initiatory, but that would not typically be understood properly either.

Answer 2

The OED also records initiative as an adjective, but I’d be surprised to find it used as such today. In your example, I think you’d have to use a different word altogether, such as enterprising.