noun
reaching age 60; dotage; second childhood
Traditional term for turning 60, when one's life cycle is said to return to the starting point of the Chinese zodiac. Often carries a nuance of entering old age or a second childhood.
祖父は本卦還りを迎え、ますます童心に返ったようだ。
My grandfather reached 60 and seems to have returned to a childlike state more and more.
Standard kanji spelling.
Variant spelling using 帰 instead of 還.
還暦 is the common modern term for one's 60th birthday, while 本卦還り is a rarer, more traditional expression with a nuance of returning to childhood.
From 本卦 (ほんけ, 'original hexagram') + 還り (かえり, 'return'), referring to the 60-year cycle of the Chinese zodiac returning to one's birth sign.