The term "bias voltage" refers to any situation where a DC voltage is combined with a variable voltage. Your example with the oscilloscope is one such example, but there are many others. You can't tell the difference between a DC voltage and a biasing voltage with a DVM because the difference is in the purpose of the DC voltage. And you can't read "purpose" with a DVM. You have to understand the circuit to decide if something is properly described as a bias. For example a power supply produces a DC voltage, but it is not a bias voltage because it is just meant to be a single constant supply voltage. Often a bias is applied to overcome some limitation in the circuit, like a transistor that will only amplify if the base is positive with respect to the emitter.