Line-of-Sight propagation is a characteristic of electromagnetic radiation in which two stations can only transmit and receive data signals when they're in direct view of each other with no obstacles in between.
Wifi is line of sight. The fact that it can penetrate a couple of interior walls doesn't change that. All frequencies have a limit to their attenuation, some more than others.
Line of sight is merely the colloquial name for VHF and up.
So what is it called if something can “only” transmit line of sight? We had a line of sight system on the farm and had to keep the tree branches trimmed or it wouldn’t work.