half-chair

https://doi.org/10.1351/goldbook.H02715
The @[email protected] of a six-membered ring structure in which four contiguous atoms are in a plane and the other two atoms lie on opposite sides of the plane.
H02715.png
See also:
chair, boat, twist
Source:
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2209 [Terms] [Paper]