Mike:
What Jayanta stated is correct - if you are labeling off a layer, it will label all features, even the ones whose symbology you have removed out of the layer via the symbology tab. To repeat, removing the symbology does not suppress the labeling of that removed feature.
A Definition Query will work, though, in removing the unwanted features AND its associated label. The trick is to know what query to set up to exclude what you want excluded.
I'd go with Jayanta's suggestion of making a new field and populating it with zeroes and ones to differentiate what you want to show from what you want to suppress. Then use a Definition Query on the layer to suppress the things you don't want shown based on those values you entered. There are also other Definition Query possibilities that could work (and may not require the addition of the field), but we would need to see more of the data to formulate an effective one.
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More examples of a Definition Query at work:
All features shown and labeled (starting state)
"P/QP" category suppressed via Definition Query. Both feature and label are now gone.
Definition Query used on layer to suppress "P/QP" category for above image.
Chris Donohue, GISP