"Foul deed" is a term used to describe an immoral or unethical act. There are several synonyms for this phrase, including wickedness, wrongdoing, transgression, evil, and misconduct. These words can be used interchangeably, depending on the context of the situation. For example, if someone commits a crime, it can be referred to as a foul deed, an act of wickedness, or a transgression. Similarly, if someone engages in unethical behavior in a professional setting, it can be described as misconduct or evil. The use of synonyms for "foul deed" can highlight the severity of the action and the need for consequences or punishment.