"To make terse"

Solution 1:

You could say that you streamlined the wording.

You could also talk about tidying up the writing.

But I actually like both tighten and edit.

e: Was rereading Steven Brust's The Phoenix Guards, and the fictional narrator describes this process thusly:

... for the past twenty-one years, we have had the honor of refining, or, if we are permitted, "honing" the notebook ...

I like both refining and honing for this process. Refining, in particular, describes reducing something to its fundamental elements. (Although Brust's usage is deliberately ironic, since the narrator is anything but terse.)

Solution 2:

I am currently infatuated with the word fettle.

fettle: v, trim or clean the rough edges of (a metal casting or a piece of pottery) before firing. (NOAD)

As the entry indicates, this applies specifically to sculpture but it can be easily applied to writing. What are you doing when you edit down a piece but trimming its excesses and cleaning the rough edges?

In full disclosure, I have never seen or heard anyone besides myself and those I have influenced to use fettle to refer to writing--I think I came across it in Cousin Bette as Balzac described Wenceslas's work process. Still, I often use it for writing. I do very little bronze casting (zero at time of writing) but I certainly write frequently. It would be such a shame to relegate such a fun word to such rare usage. I also am always a fan of a little metaphoric language.

Solution 3:

The missing piece with these answers is that they aren’t accounting for the qualitative connotation of “terse”—it implies tension between the speaker and audience, so it isn’t quite synonymous with words like “succinct.” I’d suggest something closer to “truncate” or “curtail”, but that might suggest a stopping point as opposed to a shortening. You might be looking for something more like “concise”, though, in which case I’d suggest “condense,” “abridge,” or “refine.” Hope that helps.