The grey-black sticky residue that forms around the perimeter of a band-aid that's been stuck to the skin for too long. Band-aid gruck often lingers after the band-aid has been removed, and it indicates where the band-aid once resided. Example: I have band-aid gruck on my knee because I left the band-aid on so long. It'll take days for it to wear off.
BAND-AID GRUCK
Meaning of BAND-AID GRUCK in English
Slang English vocab. Английский сленговый словарь. 2012