The problem is that there are two definitions of inflation/deflation which are used by different people. There is monetary inflation, measured by the total amount of money in the economy, and there is price inflation, measured by the change of price of everything. Usually if you have monetary inflation you will also have price inflation, but it does not always happen that way. Bitcoins are an example of monetary inflation (25 new bitcoins are added every 10 minutes), but at the same time we have price deflation.
I'd rather go for appreciating/depreciating currency instead of deflationary/inflationary currency, which is what most people actually mean. This would be much more intuitive for an average Joe and easier to explain without losing the accuracy of the notion behind it. So we wipe out the possible misunderstanding caused by different definitions of inflation/deflation you rightly refer to (and probably would give rise to new terminological tensions)...