Your definition is correct, but Real-time can mean different things in different contexts.
For instance, I never hear anyone argue when a Demoscene production is called "real-time" (as they nearly always are), that it should in fact be called "soft real-time" (which is what they really are in the context you're talking about--framerates can drop).
So while you're technically correct (the best kind of correct), failing to acknowledge it's perfectly acceptable to use the term "real-time" in other contexts as well, is just going to make you pedantically correct (which is not a very good kind of correct).
For instance, I never hear anyone argue when a Demoscene production is called "real-time" (as they nearly always are), that it should in fact be called "soft real-time" (which is what they really are in the context you're talking about--framerates can drop).
So while you're technically correct (the best kind of correct), failing to acknowledge it's perfectly acceptable to use the term "real-time" in other contexts as well, is just going to make you pedantically correct (which is not a very good kind of correct).