British & Australian, humorous someone who has a romantic or sexual relationship with a much younger partner.
He's three years younger than you? You cradle-snatcher!
cradle-snatcher
noun a person who has a noticeably younger lover. Also known as a 'cradle-robber' US, 1907
cradle-snatcher
A jocular term for someone who is romantically involved with a much younger person. Dating sites seem to be filled with nothing but cradle-snatchers looking for women who are 20 years younger than them.