Tax credits or tax breaks as they are often referred to are absolutely considered subsidies because they represent an amount of money that would have been collected.  The taxing entity in this case is subsidizing the specific venture and giving it an advantage by reducing the cost as compared to other venture that do not have the tax break.  Take mining on federal land.  That industry still enjoys a benefit/subsidy granted to them since 1874 whereas when they lease federal land they pay $5/acre where all other industries have to lease land at the going rate.  Obviously the federal government is subsidizing that industry over the others as it pertains to operations on federal land.
BTW, because the only federal subsidy that solar receives is the Investment Tax Credit and wind receives the Production Tax Credit, by your definition neither one of them receives any subsidy.