One of many euphemisms for "masturbation" (e.g. slappin' the salami, jack off, beat off, buffing the bishop, glean the obscene bean, choking the chicken, spanking the monkey, waxing the wonker, greasing the guppy, shooting putty at the moon, and Rosie Palmer and her Five Sisters doing the Four Knuckle Shuffle.
Frank will be a little bit late. He's still back at his house jackin' the beanstalk.
An Arkansas Beanstalk is when a man has numerous ticks on the shaft of his penis so that when it gets erect and the ticks swell with blood it looks like a beanstalk. This can provide his partner with unbelievable pleasure as the ticks provide pressure points similar to ribs on a condom.
Man, last summer after the corn harvest I had an Arkansas beanstalk that took three days for the old lady to work out. I gotta tell you though, she cant wait till next year's harvest.