First be sure to find any non-relevant matches you might now want to be showing up for.
What martinibuster is getting at, is that you want to use negative keywords to your advantage. This is excellent advice in my opinion. Perhaps even essential to success with single word keywords.
The subject of negative keywords comes up often in this forum, so you'll find lots of information here, and info is also available in the AdWords FAQ. Two related links are below:
What are keyword matching options?
[adwords.google.com...]
How do I apply negative keywords across my account?
[adwords.google.com...]
You might also find this one valuable:
What are the steps to creating a keyword list?
[adwords.google.com...]
AWA