1.
being left behind, being abandoned, being excluded
The state of being left behind by others who have moved on. Can refer to physically being left somewhere or figuratively being excluded from a group activity or social trend.
Usage
Most commonly used in the pattern 置いてけぼりにされる (to be left behind) or 置いてけぼりを食らう (to get left behind). The word has a childish, colloquial nuance and conveys a sense of being unfairly excluded or forgotten.
Etymology
Derived from 置いていく (to leave behind) with the suffix ぼり. Also written as 置いてきぼり.