If we considered anyone with a severe illness to be "terminal", then chronic obstructive lung disease would be "terminal", and we would have millions of "terminal" people in this country. Same for serious heart disease, slow growing cancers, and some benign tumors. People would be touted as being "terminal" for 30-40 years. The term in fact, has some very definitive meanings and should not be bandied about in an inaccurate manner for whatever reason the person might have for doing so.
"A patient who has such an illness may be referred to as a terminal patient or terminally ill. Often, a patient is considered to be terminally ill when the life expectancy is estimated to be six months or less, under the assumption that the disease will run its normal course. A patient with a slowly progressing disease, such as AIDS, may not be considered terminally ill because the best estimates of longevity were greater than six months."
Since AIDs is fortunately now no longer considered a terminal disease for most people in the US due to expanded treatment options, it is beneficial for those claiming to be terminal to ask their doctors if they are expected to die in 6 months. If not, then live. Live well and without falsely embracing terms that have a very specific meaning if those terms do not apply.