My gut instinct would be to shy away from putting something like that on a resume. You're better off leaving the gap and explaining it honestly upon being asked.

Or if you do decide to add it, make sure to throw on there the customer support phone # of the site you play at, so that the employer can confirm that you preferred playing poker over finding a new job.

Well, maybe ignore my latter statement. (I don't blame you though...I'd much rather be playing poker.)