Is there a specific term for that red circular symbol with a line going through it at a 45 degree angle that indicates “no [fill in blank] allowed”?
The ISO (International Organization for Standardization) 7010 defines it as the General Prohibition Sign.
https://www.iso.org/obp/ui/#iso:grs:7010:P001
Wikipedia calls it a “No” symbol.
I’ve seen it referred to as a “prohibitory.”