The act of involuntarily defecating in one's sleep, and rolling over the fresh produce until it is thinly and evenly spread over the mattress. Normally happens after a Guinness/curry combo.
Adam won't have more than three pints of Guinness on a curry night for fear of tarmaccing.
The act of defecating onto another person, and wiping the faeces into a smooth surface across their body. At this point, it is popular to add "double yellow lines" of urine, or "white lines" of semen.
"Afsana enjoys tarmaccing with a horse"
"After the picnic, the children went back to the cottage for some tarmaccing"