ictus

Ictus, ictus is fourth declension masculine, a verbal noun from ico, "to strike", so it is literally "a striking". The declension matters because the nominative singular ictus and the nominative and accusative plural ictus are spelled identically; only the verb agreement or a case-marked neighbour tells you which you have.

Beyond weapons it covers a stroke of lightning, the sting of an animal, and in metrics the beat of a verse foot, which is the sense English borrowed for ictus in prosody and, later, in medicine for a stroke. Two idioms worth knowing: sub ictu, "within striking distance", and ictus oculi, "the blink of an eye", the standard way of saying "in an instant".