happy-go-lucky person; easy-going person; optimist
Describes a person who is carefree, relaxed, and not easily worried. Often used in a mildly positive or teasing way.
He is a happy-go-lucky person and is always smiling.
Because she's an easy-going person, she's calm even before an exam.
Standard spelling using the kana for のんき and the kanji 者 for 'person'.
Ateji kanji spelling; rarely used in modern writing.
のんき is an ateji reading of 呑気, originally from Chinese. 者 is a suffix meaning 'person'. The exact historical derivation of のんき is uncertain.