increases your Pokémon's Defense statistic by an amount equal to its
initial value. Thus, the first use of this attack results in double the
normal Defense score. The second use results in triple the normal Defense
score, while the third use results in quadruple the normal Defense
score. Effects are cumulative for a maximum of three uses. Further uses
have no effect.
Note that like other statistics, Defense has a maximum value of 999.
If a use of this attack would raise your Pokémon's Defense beyond 999,
it will instead raise it only to that value. If its Defense has already
reached 999, this attack will fail.
Also note that since the attacker's Defense statistic is altered, only
protection from Physical attacks, such as Swift and Dig, will
be increased. No protection is afforded against damage caused by Special
attacks like Psychic and Solarbeam.
For more information on the different kinds of attacks and how damage
is determined for each of them, see the Attack Base Explanation.