Merriam-Webster Dictionary piled on Monday to the United Airlines public relations nightmare, giving the Chicago-based air carrier a public lesson on the meaning of "volunteer."

The embarrassing moment came after video surfaced on social media showing a Chicago aviation officer literally dragging a paying customer off a flight from Chicago to Louisville because United overbooked the flight. In a statement issued by the airline, a representative said the flight crew "looked for volunteers" to deplane, but that no one was willing to budge.

Customers were reportedly offered $400 to switch to another flight so that four United flight attendants who needed to get to Louisville could take their seats. When none of the passengers accepted the deal, the airline offered $800. Still, no one agreed to get off the plane. That's when the airline took matters into its own hands, having four random passengers removed from the plane, one of whom was violently dragged off the aircraft in the now-viral video.

"After our team looked for volunteers, one customer refused to leave the aircraft voluntarily and law enforcement was asked to come to the gate. We apologize for the overbook situation," a representative for United said.

On Monday night, Merriam-Webster took issue with the airline's use of "volunteer."

"'Volunteer' means 'someone who does something without being forced to do it,'" the dictionary tweeted.

Other social media users chimed in, mocking United for its tactics.

Others applauded the dictionary's epic trolling:

(H/T: The Hill)