1. swiftboat - Noun
2. swiftboat - Verb
A type of gunboat used by the United States military on inland waterways.
(usually used attributively) A smear campaign based on specious claims.
(US, politics, derogatory, transitive) To attack a politician with specious claims.
(by extension) To smear; to attack someone or something's reputation using slander, misrepresentation, or false accusations.
Source: en.wiktionary.org