A dark substance composed of melting snow, dirt, spilled beer, and a powerful mix of other excretions and spillings that stained SUNY @ Oswego students' shoes/boots after an evening imbibing at such places as Broadwell's and Buckland's (mid 80's through early 90's).
Doug: Yo, Dave, what the fuck is on your boots?
Dave: It's gack from Broadwell's last night.