Dictionary:

syllogistic

  (sĭl'ə-jĭs'tĭk) also syllogistical (-tĭ-kəl)

Of, relating to, resembling, or consisting of a syllogism or syllogisms.

Verlyn Klinkenborg, the "editorial observer" of The New York Times, mused on the vastness of time, then launched a broadside at the theory of intelligent design, which, he wrote:

"is not a theory at all... but a well-financed political and religious campaign to muddy science... Its objections to evolution are based on syllogistic reasoning and a highly selective treatment of the physical evidence. "

Link: Grasping the Depth of Time as a First Step in Understanding Evolution

Posted August 24, 2005.

See our Word Overheard blog to see interesting uses of strange words.

For more information on syllogistic, visit Britannica.com.

The adjective has one meaning:

Meaning #1: of or relating to or consisting of syllogism
  Pertains to noun: syllogism (meaning #1)