The source MIB leaves this counter's DESCRIPTION clause empty, so this reading is inferred from the object's name, its Counter syntax, and its position alongside dnsResQueriesSent, dnsResGoodResponses, and dnsResTimeouts in the same per-server row. Read this way, it most likely tracks the number of DNS queries to this host that could not be sent at all, for example due to a local socket or routing error, as distinct from queries that were sent but timed out or received a bad response. Admins should treat this interpretation as inferred rather than as documented device behavior.