A redoubt is a fort or fort system usually consisting of an enclosed defensive emplacement outside a larger fort, usually relying on earthworks, though others are constructed of stone or brick.
Look up innuendo in Wiktionary, the free dictionary. An innuendo is an hint, insinuation or intimation about a person or thing, especially of a denigrating or a derogatory nature. It can also be a remark or question, typically disparaging (also called insinuation), that works obliquely by allusion.
Coercion means people are exposed or doing something against their will. So if public sex is on the menu, try a public place where people know sex is part of the environment, like a sex club. A park might have nonconsenting people present, and you are likely breaking the law.