Without a preparatory layer of dead colour; without underpainting. Also occasionally as noun: this method of painting.
alla prima/ˌalə ˈpriːmə/ /ˌalə ˈprʌɪmə/ /ˌɑːlə ˈpriːmə/
Early 19th century; earliest use found in London Literary Gazette. From Italian alla prima, literally ‘at first, at once’ (apparently not recorded earlier as a technical term in painting in Italian) from alla + prima, feminine of primo.