Depends on who’s ranting.
Some here get upset if you offer the going rate for a gun you might think is worth much more, be it customized or you just paid too much.
Others think it means someone offered 1,5,20,50% less than asking price.
I’m sure others will chime in.
In reality it’s just a way to describe someone not getting offered the price they want.
Anything less than my asking price and the mood I’m in at the time determines a lowball definition. I am always accurate though when I determine just what a lowball offer is. I hope this is very clear.