The opposite of overused.
A word that you had in your daily vocabulary but somehow forgot. It might even got overused but because you haven't used it in a long time it got underused again
Guy1: There's a wet t-shirt contest in the hotel.
Guy2: Epic!
Guy1: They're still looking for 3 judges btw.
Guy3: We gotta register as judges.
Guy1: Already done guys, and guess what we were already picked
Guy2&3: Legendary!
Guy1: Guys that's not legendary, that's fucking ZEDERN!
Guy2: God totally forgot zedern, totally underused :P
While Bob was not the sharpest pencil in the drawer, he WAS always able to report his tasks as under control and underdue in project status meetings. He did this by providing excessively estimates for his portion of the work at planning time.