What I mean is that there is no universal definition of which properties are safety properties. In principle, you can define any property you can formally reason about as a safety property. Therefore, whenever you talk about safety, you first have to define which properties you mean by that.

In the context of Rust, there are a number of safety properties that Rust guarantees (modulo unsafe, FFI UB, etc.), but that set of safety properties is specific to Rust and not universal. For example, Java has a different set of safety properties, e.g. its memory model gives stronger guarantees than Rust’s.

Therefore, the meaning of “language X is safe” is entirely dependent on the specific language, and can only be understood by explicitly specifying its safety properties.