Martian traffic is a common term among network engineers (or at least among the ones who work at/with ISPs): https://en.wikipedia.org/wiki/Martian_packet
It relies on the page Reserved_IP_addresses, implying that a martian is a packet with a source address within certain ranges. In fact a martian is a packet with a source address for which the receiving interface isn't configured; any address could be a martian, depending on how the interface is set up.
Hey, if I'm wrong, please set me straight.
What you're talking about is referred to as source address validation [2] also known as strict reverse path forwarding (RPF) [3].
[1] https://datatracker.ietf.org/doc/html/rfc1812#section-5.3.7
[2] https://datatracker.ietf.org/doc/html/rfc1812#section-5.3.8
[3] https://datatracker.ietf.org/doc/html/rfc3704#section-2.2