Question: What adjective (single word) means 'having/using a willingness to learn'?

Answer: 
How about *curious*?

> 
> * having a desire to learn or know more about something or someone
> * marked by desire to investigate and learn
> * eager to learn or know; inquisitive.
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Or inquisitive ^
"Enthusiastic" is the best word that comes to mind for me. Doing is sort of like learning, so it is similar enough.