"Curtain side" refers to a type of truck or trailer that has a side made of curtains instead of a solid wall. These curtains can be easily moved aside to load or unload goods, providing convenient access. Full definition
And roof - mounted curtain side - impact supplemental air bags help provide head protection. (nissanusa.com)
These rollover - capable head curtain side air bags stay inflated longer than air bags developed only for side impacts because rollover incidents can last longer. (speedsportlife.com)
In the 2009 model year, front and rear head curtain side airbags became standard except in cars sold to fleet buyers that could still be ordered without side airbags. (iihs.org)