1. The cardinal number equal to 5 + 1.
2. The sixth in a set or sequence.
3. Something having six parts, units, or members, especially a motor vehicle having six cylinders.

at sixes and sevens

1. In a state of confusion or disorder.

[Middle English, from Old English.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.