At Answers.com they say:
1. An inference or conclusion that does not follow from the premises or evidence.
2. A statement that does not follow logically from what preceded it.
[Latin nōn sequitur, it does not follow : nōn, not + sequitur, third person sing. present tense of sequī, to follow.]
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.
Yup. Knew that. But I am surprised to learn after all these years that I was spelling it wrong!! I had thought that it ended with an “-or”!!