Is this actually a definitions problem?
No. In almost every business where this argument runs hot, a written definition already exists. Someone wrote it, everyone agreed it, and the argument continues anyway.
That is the tell. When a documented standard fails to settle a dispute, the dispute is not about the standard. It is about what each side loses by applying it. An SDR who books a meeting the AE rejects has lost a day's work and possibly a commission event. An AE who accepts a meeting that goes nowhere has taken on a cost of their own. Both are behaving rationally inside the system they have been placed in.
So the useful question is not "what is a qualified meeting" but "what does each person forfeit by calling this one qualified". Answer that and the rest follows.
Cause one: the comp plan builds the tension in deliberately
This is the most common of the three by some distance. If your SDR is compensated on opportunities created, and your AE is not compensated on pipeline created, you have designed an unconstructive tension into the revenue function on purpose.
One party is rewarded for volume passing through the gate. The other carries the consequences of what comes through it and gains nothing for opening it. Both are doing exactly what you asked. The friction is not a people or culture problem; it is the plan working as written.
The test is simple. Look at the two plans side by side and ask what each person is paid for at the precise moment a meeting is accepted. If one gains and the other only risks, you have found it.
Cause three: your system cannot record a slow deal as progress
Some deals close in three or four months. Some take nine. Plenty of businesses sell to both types at once.
Most CRM configurations are not set up to capture the long-term development of an account, so anything that moves slowly looks indistinguishable from something that has stalled. An opportunity that is genuinely progressing towards a close in nine months shows up as ageing pipeline, and ageing pipeline gets closed out in the quarterly tidy-up.
This is usually described as an enterprise problem. In practice it appears just as often in smaller businesses with smaller clients who simply buy slowly. The deal size is not what determines it. The buying process is.
If your system has no way of saying "this is on track and it is long", your SDRs will stop creating those opportunities, because they watch them get deleted.
So what do you actually change?
Start with the comp plans, because that is the most common cause and the most tractable. Put the two plans on one page and find the moment where one party gains and the other only absorbs risk.
Then look at how you measure your AEs, and ask whether a win rate target is silently raising the qualification bar. Then look at whether your system can represent a slow deal as a healthy one.
None of that is a definitions exercise. Which is why the definitions exercise never worked.