What is Blackflagged?
1.
a strong suggestion to avoid a person at all costs.
Behind Susie's back Wilkie formed the two-fingered x sign above her head - blackflagging her in no uncertain terms to Jimmy who had approached unsuspectingly with the intention of spading her.
See
2.
To have poisoned insects or critters. Derived from a trademark named insecticide.
Yolanda blackflagged her crabs with lindane.
