so thin as to transmit light; "a hat with a diaphanous veil"; "filmy wings of a moth"; "gauzy clouds of dandelion down"; "gossamer cobwebs"; "sheer silk stockings"; "transparent chiffon"; "vaporous silks"
(of animals especially human beings) having arrived at the onset of puberty (the age at which sex glands become functional) but not yet fully mature; "the budding breasts of a pubescent girl and the downy chin of pubescent boy"