One night every month, panthers go out for a special meal: they eat a woman in her sixties.

it means social event frequented by more mature women milfs, supposedly on the lookout for casual sex. e.g don't go to the club on a Thursday, it is grab a granny night cowboy...

Nice description Roi G... copied word for word from the urban dictionary though See here: http://www.urbandictionary.com/define.php?term=grab+a+granny Lots of interesting stuff on this webpage, A night at the museum (see 3rd defintion on page above) was a a new one for me:-) one important thing about the phrase is that age is relative to the person looking. If the person looking for a 'partner' is 20 then a 30 year old woman would count as a 'granny' even though in reality she is very unlikely to be a grandmother or look like one.

maybe for example : Yesterday I spend my time on a grab-a-granny night. I celebrated a birthday of my grandmother or one of my aunts. ;o)

that sounds like sexual assault on the elderly :P