I agree with this definition as "alien" is usually used. One could also say they originated in our physical universe. However, some people would see something as "alien" because it is either unlike us or unknown to us.
By the way, God didn't originate anywhere.
Actually, origin or lack of origin is irrelevant to the definition of alien.
The entity referred to as "Q" in the Star Trek New Generation TV series seems to be immortal and lack origin and he is considered an alien as well as all his other eternal seemingly almighty Q ""brothers" who dwell in what is referred to as the Continuum.
Even humans who are imagined to eventually undergo extreme biological modifications in order to be better adapted to alien environments would soon be considered aliens if those modifications made them drastically different from the common-variety of humans on Earth.
In stark contrast, it would be deemed blasphemy or disrespectful if applied to our heavenly father. In fact, even when applied to angels who share his spirit nature albeit lack his eternal one it seems inappropriate from a Christian viewpoint.
Why? Because although God is described as our heavenly father and angels are called sons of God and so are we. So we tend to view them as family, as our elder brothers. As brothers we share the faculties which God has bestowed on his children, the ability to reason, love, attain wisdom and a power over nature far above the ability of creatures which are referred to as animals.
BTW
This reminds me of a short story I read concerning a space expedition with a mission to investigate the nature of a recent supernova explosion that had bathed an orbiting planet with deadly radiation. While on that mission they discovered the remains of a non-human civilization that had been wiped out. All the evidence indicated that the aliens involved seemed to have been caught totally by surprise.
Later, they human expedition crew encountered a spacecraft of a race of aliens who were also examining the black hole remnants of the supernova and who had had escaped the devastation by moving their planet's population a safe distance away.
Strangely, this triangular-headed three-eyed narrow-lipless slit-mouthed alien race had known about the impending disaster but had not bothered to warn the other though they had been in contact for centuries during which a brisk trade was established and flourished.
When asked why they had NOT taken time or made absolutely no effort to warn the other aliens of the impeding danger, after a prolonged silence during which time they seemed utterly confused by the question, they responded in the following way:
"Why should we have warned them? They were as nothing to us!"
True, they were grotesque and bore absolutely no resemblance to humans. However, it was their complete inability to feel compassion which really separated them from being our spiritual brothers and not their appearance.
The same concept is conveyed in the film, Village of the Dammed starring Christopher Reeves. The children involved appear outwardly fully human. But as the minister in the film explained in one of his sermons to the harassed village people-the children bore the OUTWARD appearance of mankind but were not of mankind due to their cruel nature which made no room for compassion.
In contrast our heavenly brothers the angels reflect the Nature of God via an innate ability to feel and express compassion and convey all of God's admirable qualities such a loving convcern for others and the willingness to extend a brotherly helping hand as God's faithful angels do.
it is for that reason that we feel uncomfortable referring to them as either extraterrestrials or aliens since those terms, though technically accurate, carry a negative connotation which they do not deserve.