Literal translation
like a stuffing
Meaning
very badly
Explanation
Very badly, said first of someone singing and then, by extension, of anyone speaking or doing anything at all. A gamato is a mason's trough, a big metal basin for mixing plaster or cement: picture the clanging sound of such a trough, and the unappetizing sludge stirred in it (gamata). The negative sense eventually overtook the original sound image and spread to any activity.