ju·ve·nile (jo?o?v?-n?l?, -n?l)adj.1. a. Not fully grown or developed; young.b. Of or characteristic of a young animal that has not reached sexual maturity: a bird still in juvenile plumage.2. Characteristic of, intended for, or appropriate for children or young people: juvenile fashions.3. Marked by immaturity; childish: juvenile behavior. See Synonyms at young.4. Geology Relating to or being water, gas, or a mineral-rich fluid believed to have originated from magma and to have come to the earth’s surface for the first time.n.1. a. A young person; a child.b. A young animal that has not reached sexual maturity.c. A two-year-old racehorse.2. An actor who plays roles of children or young persons.3. A children’s book.[Latin iuven?lis, from iuvenis, young; see yeu- in Indo-European roots.]ju?ve·nile?ly adv.ju?ve·nile?ness n.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.juvenile (?d?u?v??na?l) adj1. young, youthful, or immature2. suitable or designed for young people: juvenile pastimes. 3. (Biology) (of animals or plants) not yet fully mature4. (Zoology) of or denoting young birds that have developed their first plumage of adult feathers5. (Geological Science) geology occurring at the earth’s surface for the first time; new: juvenile water; juvenile gases. n6. (Biology) a juvenile person, animal, or plant7. (Theatre) an actor who performs youthful roles8. (Literary & Literary Critical Terms) a book intended for young readers[C17: from Latin juven?lis youthful, from juvenis young] ?juve?nilely adv ?juve?nileness nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ju?ve?nile (?d?u v? nl, -?na?l) adj. 1. of, characteristic of, or suitable for children or young people: juvenile interests; juvenile books. 2. young; youthful. 3. immature; childish: juvenile tantrums. n. 4. a young person; youth. 5. a. a youthful male or female theatrical role. b. an actor or actress who plays such parts. 6. a book for children. 7. a young bird when first fully feathered and before reaching maturity. 8. a two-year-old racehorse. [1615?25;