A social party with men and/or male-related activities. Although some people propose that it be only an all-male gathering, some ManDates do include women, and the ManDate just signifies the partaking of male-oriented activites.
"Hey, let's go play some football with the dudes."
"All right, it's a ManDate!"
"Can we come?"
"No girls allowed, it's a ManDate."
"Hey, bring your girlfriend for the Superbowl party next weekend."
"Is there beer?"
"Yup, it's a ManDate, dude!"