a group or gathering of three or more lesbians. The term is a portmanteau of the words "birkenstock" and "flock." Birkenstock refers to the footwear commonly worn by dykes & lesbians.
When we were at Home Depot, there was a huge birkenflock of dykes standing out front near their pickup trucks.
A group of people wearing Birkenstocks. Much like a flock of birds, Birkenstock wearers tend to congregate in large groups.