bairn, bambino, buster, changeling, fosterling, imp, kiddy, kindergartener, kindergartner, monkey, orphan, peanut, picaninny, piccaninny, pickaninny, preschooler, rapscallion, rascal, scalawag, scallywag, scamp, silly, sprog, toddler, tot, urchin, waif, yearling.
Your query has returned 421 words, which include anagrams of youngster as well as other shorter words that can be made using the letters included in youngster.
The words in this list can be used in games such as Scrabble, Words with Friends, Wordscapes and other similar games.