Wiktionary
cyclooctene
n. (context organic compound English) A cycloalkene having eight carbon atoms and one double bond
Wikipedia
Cyclooctene
Cyclooctene is a cycloalkene with an eight-membered ring. It is notable because it is the smallest cycloalkene that can exist as either the cis- or trans- isomer with the cis-isomer more common. Its most stable cis stereoisomer can adopt various conformations, the most stable one being shaped like a ribbon; its most stable trans-conformer is shaped like the 8-carbon equivalent chair conformation of cyclohexane.
Cis-cyclooctene3D.png
cis-Cyclooctene
trans-Cyclooctene