What is a good, short, word to describe a software engineer?
In increasing order of formality:
Coder refers to someone who engages in the act of writing source code, and has a very casual, possibly even negative connotation.
Programmer refers to someone who writes software, which has a neutral connotation.
Developer or dev refers to someone who develops software, which may or may not involve actually writing it, but probably does.
Software engineer and computer scientist are more formal terms for those with degrees or other professional qualifications.
SE is a commonly used abbreviation in speech for a software engineer, but CS is only used for computer science itself, not the people who practice it.
The best single-word answer especially if they're writing the software is programmer. But developer is just as good and blurs the lines beyond programming into things such as beta testing or internationalization.
Multi-word terms sound more formal and are usually more specific. As well as your software engineer there is also computer scientist.
Coder is a word a lot of programmers would use to self-describe but I've learned from this discussion that among some people at least it carries a negative connotation I had never been previously aware of.
"Hacker" used to be the preferred term, back before stupid newspaper folks got hold of it and decided to use it exclusively for malicious people who break into networked computers. Evidentally, those were the only kinds of hackers they had any interest in. :-(
We fought this for a while, but it is really tough to win a war of words with people who buy ink by the barrel.
So now, as the other answers indicate, we are sort of casting about for new terms. Where I work, the term "developer" is used. However, if you use that among the general public, people might think you are talking about someone who builds houses for a living. So I generally just say "Software Engineer". If eyes cross, I elaborate this way: "I spend my days telling computers what to do. Then they tell me to F-off, and I spend the rest of the day trying to figure out why."