tac-au-tac

from The Century Dictionary.

• noun In fencing, the combination of a sharp, rattling parry and a riposte, in contradistinction to a riposte delivered from a position of quiet touch with an opponent's blade; also, contre-ripostes, a set of attacks and parries rapidly following one another between two fencers of very equal skill, prolonged without a point to the credit of either.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Fencing) The parry which is connected with a riposte; also, a series of quick attacks and parries in which neither fencer gains a point.