emphasis You use indescribable to emphasize that a quality or condition is very intense or extreme, and therefore cannot be properly described. her indescribable joy when it was confirmed her son was alive = inexpressible + indescribably in·de·scrib·ably indescribably filthy conditions. something that is indescribable is so terrible, so good, so strange etc that you cannot describe it, or it is too difficult to describe
to an inexpressible degree; "she was looking very young tonight, and, as usual, indescribably beautiful, in a simple strapless dress of a green and white silky cotton"