I think those indicate a cell phone that is being used as a hot spot.
That sounds plausible. Apparently my phone can then distinguish a ‘personal hotspot’ (internet tethering over wi-fi) from a regular wi-fi router. Which is impressive, unless that nature is broadcast along with the SSID.
a common symbol to use to describe "paired".
The symbol did show in a list “Select a Wireless Network”, while having “Ask to Join Networks” turned on (=seek alternatives for 4G). I was in a new location, and pretty sure I had not paired with any devices there previously.