Settle a bet: Mach speeds

When knowledgeable people speak of a vehicle going "X Mach" they are
referencing the speed of the vehicle compared to the speed of sound at
local conditions, right?

I ask because I've heard NASA folks mentioning that the Shuttle, at some
point in it's descent, is going Mach 25. I claim that means the vehicle
is going 25 times faster than Mach at that particular pressure and temp
where the Shuttle is, while someone else claims NASA means 25 times the
sea level value of Mach, even though the Shuttle is in the very upper
atmosphere at the time.

I know to discount what reporters say, but I'm referring to engineers
and their official spokesmen.

BTW, I understand the definition of Mach references local conditions.

--
Scott
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It's not a coincidence that pictures that would inflame the Americans to
war are not shown extensively while those pictures that undermine our
will to fight are shown ad naseum.