1. [adj]  (of illness) developing slowly or of long duration
2. [adj]  drawn out or made longer spatially; "Picasso's elongated Don Quixote"; "lengthened skirts are fashionable this year"; "the extended airport runways can accommodate larger planes"; "a prolonged black line across the page"
3. [adj]  relatively long in duration; tediously protracted; "a drawn-out argument"; "an extended discussion"; "a lengthy visit from her mother-in-law"; "a prolonged and bitter struggle"; "protracted negotiations"

PROLONGED is a 9 letter word that starts with P.