n. An edged and pointed weapon for thrusting, shorter than a sword, and used, commonly in connection with the rapier, by swordsmen in the sixteenth and seventeenth centuries, held in the left hand to parry the thrust of an adversary's rapier.n. Any straight stabbing-weapon, as the dirk, poniard, stiletto, etc.n. In printing, an obelisk; a mark of reference in the form of a dagger, thus: .n. In entomology, the popular name of several noctuid moths of the genus Acronycta: so called from a black dagger-like mark near the inner angle of the fore wings.n. In Sollas's nomenclature of sponge-spicules, a form of the sexradiate spicule resulting from reduction of the distal ray and great development of the proximal ray.n. plural In botany: The sword-grass, Phalaris arundinacea, or perhaps Poa aquatica.n. The yellow flag, Iris Pseudacorus.n. Dagger of lathn. Double daggerTo pierce with a dagger; stab.To provide with a dagger.To dagger arms. See arm.n. In ship-building, any timber lying diagonally.