Any LaTeX editor can accommodate this style of auto-completion by means of macro definitions. It is probably the fastest way to perform this without having to switch from your existing editor to a new/different one. In my opinion, it is flexible, transferable and accommodates a host of variability that you may require based on (say) conditional support from LaTeX packages.
Since the replacement text is typically used inside regular text, the xspace
package is of great help. It inserts a space after a command sequence only if it is followed by a space. This is a common issue with using command sequences in regular text. For example, A \TeX command sequence.
will expand to A TeXcommand sequence.
since the space represents the end of \TeX
and is therefore gobbled. xspace
is the way around this:
\documentclass{article}
\usepackage{xspace}% http://ctan.org/pkg/xspace
% Definitions for words to auto-complete
\newcommand{\sync}{synchrocyclotrons\xspace}%
%...
\begin{document}
What mighty \sync you have, sir! Get me one of those \sync.
\end{document}

If you change your mind (to quote ABBA), you can just change the macro definition. It would probably be the same amount of effort to do this than it would to modify the auto-completion segment provided by such an editor.
To go one step further, you can even define your macros to have (say) starred version *
which expand to the plural form if use, otherwise it uses the singular form:
\documentclass{article}
\usepackage{xparse}% http://ctan.org/pkg/xprase
\usepackage{xspace}% http://ctan.org/pkg/xspace
% Definitions for words to auto-complete
\NewDocumentCommand{\sync}{s}{%
synchrocyclotron\IfBooleanTF{#1}{s}{}\xspace
}
%...
\begin{document}
That's a huge \sync! There are plenty more \sync* over there.
\end{document}

The xparse
package provides an easy interface for working with starred versions of commands/environments.
\blahblah...
? I know that's a very technical command.:-|
– Werner Oct 16 '11 at 17:19\sync
that expands "What mighty \sync you have, sir!
" to "What mighty synchrocyclotrons you have, sir!
". Any LaTeX editor can do this, but it is restricted to control sequences/commands (prepended with ``, in the general sense). – Werner Oct 16 '11 at 18:26