Exact meaning of "star" for laypersons, meaning a celestial object?

I think it's important to consider the historical understanding of what a star is. In astronomy today, we consider a star to be:

Wikipedia: an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.

Of course, in ancient times, people had no concept of plasma or gravity; they just looked up in the sky and saw a bunch of pretty lights; some of them wandered around the sky (planets, which as @NigelJ points out, comes from the Greek wandering star); some of them seemed to fall to Earth; etc. So, historically, we didn't really make distinctions among the objects in the sky; they were all stars. (And, of course, there were no space stations in ancient times).

With the invention of telescopes in the early 1600s, we could begin to see that some of the night-time objects were quite different; for example, we could see the moons of Jupiter, and the rings of Saturn. We could also tell that some objects were much closer.

As science continued to develop, we began to study the composition of planets and stars. There's actually a number of pertinent questions on some other Stack Exchange sites you might be interested in:

• Who first distinguished planets from the stars?
• When & how was it known that our Sun is the same thing as the night time stars?
• When and why did the 'spiky star' appear as an image in art and science?
• When did we know the color/appearance of all the planets in our solar system?
• When did people first recognize the estimate sizes/scales and nature of celestial bodies?

I would argue that, at least in English, the word star, by itself, generally refers just to Wikipedia mentions: an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. As you note, the [wictionary] entry also defines star as:

any small luminous dot appearing in the cloudless portion of the night sky, especially with a fixed location relative to other such dots

(emphasis mine).

The term star can today refer to other things: There's different star-shapes we can draw. And we refer to things like shooting stars (meteoroid), the morning/evening star (Venus), etc.

As with anything, the term star may be used a bit more loosely in colloquial vs. scientific settings; however, I believe most people understand the term (by itself) to refer to astronomical stars. That being said, it's important to avoid over-the-top prescriptivism: Don't call Venus the Evening Star: It's a planet! just makes you sound like a tool.