Sick Out - (noun)
A sick-out is when a significant number of trade union members falsely call in sick on the same day. It can be an effective way of showing the employer what it would be like if they were to go on strike.
Source: Adapted from YourDictionary
Example of Use: The police force, who aren’t allowed to go on strike, have sometimes staged a sick-out (or ‘blue flu’) to put pressure on the government.