You can do like this - just change the code inside ShouldIndex to what you would like 

ContentIndexer.Instance.Conventions
     .ForInstancesOf<VariationContent>()
     .ShouldIndex(x => ShouldIndex(x));

bool ShouldIndex(IContent content)
 {
     var ancestors = _contentLoader.GetAncestors(contentLink).OfType<FashionNode>();
     if (ancestors.Any(c => c.Name == "Mens"))
     {
         return false;
     }
     return true;
 }

Thank you Quan! 

I will try this solution. :) 

I have other scenario, how shall I do to hide the customer specificed products in search result?

When a customer login, he has customer specified products and he should be able to search it but not anonymous user.

The new question should be in a separate thread. To you can always filter the search result by adding a property - for example ForRegisteredUserOnly, and use that to filter with Find 

Sorry, I will open a new thread next time. 

Thanks for the tips!