It's quite possible for (any) hyphenation of a particular word to seem "completely wrong", so that you want to prevent it being hyphenated.
If the word occurs in just one place, put it in a box:
\mbox{oddword}
(Plain TeX users should use \hbox, and take care at the start
of paragraphs.) However, boxing the word is not really advisable
unless you are sure it only occurs once.
If the word occurs commonly, the best choice is to assert a non-hyphenation for it:
\hyphenation{oddword}
This hyphenation exception (with no break points) will be used in
preference to what TeX's hyphenation algorithm may come up with.
In a multilingual document, repeat the exception specification for each language the word may appear in. So:
\usepackage[french,english]{babel}
\selectlanguage{english}
\hyphenation{oddword}
\selectlanguage{french}
\hyphenation{oddword}
(note that babel will select the default language for the
document - English, in this case - at \begin{document}.)
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=wdnohyph