The ability of old men to molest women by performing actions that would get younger men thrown in jail. But because old men "don't know better" women find it funny, cute and flattering and embrace it openly - likely because they know the man molesting them doesn't have a functioning penis.
Grandpa was clearly utilizing his Old Man Immunity when he was hitting on the waitress and grabbed her ass in jest.
by WindBoner February 8, 2012
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