That’s not bad, but I prefer to compare tax avoidance, which is hard to define, with tax compliance which I find easier to define. Tax compliance is seeking to pay the right amount of tax (but no more) in the right place at the right time where right means that the economic substance of the transactions undertaken coincides with the place and form in which they are reported for taxation purposes.
In that case tax avoidance happens whenever someone chooses a course of action which results in the wrong amount of tax being paid, in the wrong place and at the wrong time.
The UK Uncut/Private Eye thing about Vodafone was that UK corporation tax had not been paid on profits made in Germany on selling phones to Germans from German shops. Given that the economic substance of this activity was in Germany then whatever tax the Germans wished to charge on this activity was the correct amount of tax to pay.
Thus Vodafone did not indulge in any tax avoidance.