If it's really critically time sensitive, and will be accessed more than 10,000 times, I'd use a hash. A bother to code, but you can't beat it for speed.
Hash function - Wikipedia, the free encyclopedia
For something simpler, I'd sort the words using C's qsort(), and then either do a binary search for any word you are looking for, on that array (or file), or I'd code up an index function (faster than binary searching, but also more work).
All three of the above ways of searching are fast. No slow pokes in the bunch:
1) Fastest - Hash
2) Faster - Index
3) Fast - Binary Search
I'm unsure what the characteristics of your own search would be. It sounds like a homegrown hash technique, which I'd not recommend for a beginner. All that depends on your own skill, and patience in proving it's accurate.