This read-only Counter counts frames received on this port that had to be dropped specifically because the receive buffer was full when they arrived, a capacity problem, not a frame-validity problem like the Long/Short frame counters. A rising count here under sustained heavy inbound traffic suggests this port's buffering can't keep pace with its offered load, a legitimate reason to consider redistributing traffic or upgrading that link rather than chasing a phantom error source. This is the receive-side counterpart to ciscoTsPortStatsOutBufOverflows.