By default when you create a SharePoint column on a list, it will generate a crawled property which is marked with Include in full-text index. This checkmark ensures you will get a hit for terms in this column. The naming of the crawled property is ows_internalColumnName.
If you look at managed properties, they have a corresponding property called Searchable. This means if your crawled property is mapped to a managed property marked as searchable, you will get recall on the column. However, if the managed property is not marked as searchable, even though the crawled property is marked with “Include in full-text” index, it will NOT be searchable.
To put it all in a table.
|Crawled Property||Managed Property|
|Included in |
|Not included in |
If a crawled property is mapped to two managed properties, where one of them is searchable, then the value will be searchable.
SummaryIn order to make a column in SharePoint not searchable, you either have to uncheck the option on the corresponding crawled property to include it in the full-text index, or map it to a managed property which is not marked as searchable.
Check out Benjamin Niaulin's post Understand SharePoint Crawled and Managed properties for search for more information on crawled and managed properties.