seven-year itch

[ sev-en-yeer ]
/ ˈsɛv ɛnˌyɪər /

noun

the temptation to have an affair, held to become a hazard in the seventh year of marriage.

Origin of seven-year itch

An Americanism dating back to 1895–1900

British Dictionary definitions for seven-year itch

seven-year itch

noun

informal a tendency towards infidelity, traditionally said to begin after about seven years of marriage