Select the most appropriate one-word substitution for the given group of words.

A speech designed to incite action 

Exhortation

The most appropriate one-word substitution for "a speech designed to incite action" is exhortation.

• Exhortation is a strong urging or appeal to do something.
• Scintillation is a brief flash of light.
• Exertion is the act of using physical or mental energy.
• Bigotry is intolerance or prejudice towards a particular group of people.