English speaking countries
Used in a humorous or ironic manner to dismiss closed-minded opinions from the baby boomer generation (people born between 1946 and 1965) and older people more generally. Often used when someone's opinion is so out-of-touch that it would take too long to explain something to them.
"If you just stopped eating avocado toast, you'd be able to afford a house in no time." "Ok, boomer."