As a noun teenager
As an adjective teenlike is
like a teenager or some aspect of one.
(countable) Literally, a person from thirteen'' to nine''teen who is in their teens; an adolescent.
Sometimes only refers up to the legal minor limit in many countries of eighteen years old, or sometimes only refers up to the point of high school graduation. In the earlier years, sometimes referred to as a youth; in later years, sometimes referred to as a young adult.
Like a teenager or some aspect of one.