A jacket that is naturally designed with a low and wide-cut neckline, not covering the shoulders or upper chest area, leaving them bare. However, this tag is very infamous for being frequently misused among the userbase for open or partially-open jackets that are worn hanging off the upper arms, regardless of how they were designed to be worn.
These are regular jackets worn hanging off the arms; they do not count as correct usages of the tag.
If unsure whether or not the clothing in question qualifies as an off-shoulder jacket, use the off shoulder tag instead.
This tag implicates off_shoulder (learn more).