fully-grownˌfully-ˈgrown British English, ˌfull-grown American English adjective 
a fully-grown animal, plant, or person has developed to their full size and will not grow any bigger: 
After six weeks, the larva emerges as a fully-grown beetle.
a fully-grown animal, plant, or person has developed to their full size and will not grow any bigger: After six weeks, the larva emerges as a fully-grown beetle.