raincoat crowd
n.— «In defense of unique Mensa activities such as the dirty adult movie group, Hume said members who attend have “no prurient interest,” they’re “not the raincoat crowd.”» —“Mensa—Those Lusty, Zestful, Devilish Brains” by Alison O’Neill Washington Post July 17, 1980. (source: Double-Tongued Dictionary)