Put the word you actually want in quotation marks. (It used to be "prefix it with +" but then Google+ happened and they changed it.)
I tried it just now with ' "median" height ' and still got "average" and "mean" results highlighted. (Couldn't reproduce with "expand"/"extend" because I didn't recall the query that produced both.)
Moreover, how is a regular human being supposed to know this? How is this useful to someone not in the tech bubble?
Google's solution to the problem is to make people jump through a hoop. That's not a solution. That's a kludge.