expression, noun
an old person's reckless act; old people doing dangerous things
An idiomatic admonishment used when an elderly person does something risky or inappropriate for their age, often implying they should know better.
When my grandfather tried to go outside lightly dressed in midwinter, I warned him, 'That's an old person's reckless act.'
八十歳でスカイダイビングに挑戦するなんて、年寄りの冷や水と言われても仕方ない。
Trying skydiving at eighty—it's no wonder people call it an old person's indiscretion.