This article is from the Fencing FAQ, by Morgan Burke with numerous contributions by others.
According to Article t.7 (old 10) of the FIE Rules of Competition,
"the parry is the defensive action made with the weapon to
prevent the offensive action from arriving".
A successful parry deflects the threatening blade away from the
target. It is normally not sufficient to merely find or touch
the opponent's blade; the fencer must also exhibit control over
it--although the benefit of the doubt usually goes to the fencer
making the parry. If the attacker must replace the point into a
threatening line before continuing, it is a remise (renewal of
the attack) and does not have right-of-way over the riposte.
However, if the parry does not deflect the blade, or deflects
it onto another part of the target, then the attack retains the
right-of-way (mal-pare' by the defender). In practice, very
little deflection is needed with a well-timed parry.
A well-executed parry should take the foible of the attacker's
blade with the forte and/or guard of the defender's. This
provides the greatest control over the opponent's blade. In
other cases (eg. a beat parry with the middle of the blade) the
parry can still be seen as sufficient if the attacking blade is
sufficiently deflected. In ambiguous cases, however, the benefit
of the doubt is usually given to the fencer who used his
forte/guard. For example, if a fencer attempts to parry using
his foible on his opponent's forte, it will often be interpreted
in the reverse sense (eg. counter-time parry by the attacker),
since such an engagement does not normally result in much
deflection of the attack. A foible to foible parry could
potentially be seen as a beat attack by the opposing fencer
depending on the specifics of the action.
At foil, the opponent's blade should not only be deflected away
from the target, but away from off-target areas as well. An
attack that is deflected off the valid target but onto invalid
target can still retain right-of-way. If the defender clearly
releases the attacking blade before the continuation of the
attack lands, then the benefit of the doubt is usually given to
At sabre, the opponent's blade need only be deflected away from
valid target, since off-target touches do not stop the phrase.
Cuts are considered parried if their forward movement is checked
by a block with the blade or guard. Contact with the blade or
guard may be interpreted as a parry, even if a whip-over touch
results. Avoiding whip-over touches altogether requires
exceptionally clean and clear parries.
At epee, a good parry is simply any one that gains enough time
for the riposte. Opposition parries and binds are commonly used,
since they do not release the opponent's blade to allow a remise.