What is lacing? How does it appear in marijuana?

Lacing is a technique used to bulk up the original product in effort to gain more profit. It happens most often in drugs that are sold by weight such as cocaine but can also be used in marijuana to enhance the psychoactive effects. Lacing in marijuana is not always intentional and the rise of its legalization within the US has created stricter regulations on the quality and content of the product. According to the American Addiction Centers, "Thus, buying laced weed is far more likely to occur when an individual buys the drug from an illicit source" (AAC). Weed is most often laced with substances such as glass, heavy metals, or other psychoactive drugs including PCP. Though it is currently not the top substance to be laced in weed, there has been a rise in cases of fentanyl laced marijuana.

https://americanaddictioncenters.org/marijuana-rehab/what-can-marijuana-be-laced-with