A "conspiracy" refers to a secret plan or action carried out by a group of people to do something harmful, unlawful, or deceitful. It usually involves plotting together and intentionally keeping their actions hidden from others. Full definition
The dark silence of conspiracy theorists was replaced with something resembling pity. (politics.co.uk)
I think some of the book is a little big in conspiracy theories. (investorjunkie.com)
If you have been charged with conspiracy in connection with a drug crime, it is in your best interest to seek advice and representation from a skilled criminal defence lawyer. (nrlawyers.com)