Puerile – Immature; behaving in a silly and childish way
To remember the definition of the word puerile, use the following mnemonic:
She did this purely to rile (puerile) me up, she's so childish.
Examples of puerile in a sentence
Kayley got drunk and she showed everyone how puerile she really was.
Your jokes are puerile and not appropriate for a man of your stature.