Ageist term dehumanizing and stereotyping persons between 13 and 19. Sometimes used to avoid logical argumentation or dismiss emotions.
Teenagerdumb is the state of thinking you're invincible and know everything. The majority of teenagers think so, will stop thinking so just as they'll stop being teenagers, and no adult thinks such things.
the time of your life(varies but usually the years between 13 and 19...can last a lifetime for certain individuals)when you know everything better than everyone, when you are invincible, infallible and immortal
her mother thought that with the passing of her daughter's 19th birthday, she would finally grow up and leave teenagerdumb