(electrical engineering) Able to operate on two different electrical frequencies. / (radio communications) Able to receive and operate on two different radio frequencies.

(of a person, potentially offensive) Having mixed racial parentage or ancestry.

(education, psychology) Twice-exceptional.

(US, military) The requirement for an incoming nuclear attack to be confirmed by both satellite and radar before retaliatory action is taken.

plural of Hodge dual

plural of Koszul duality

(mathematics) Any of various kinds of duality found in representation theory of Lie algebras, abstract algebras, and topology.

dual-band

(Taoism) The process of cultivation involving sexual intercourse between a man and a woman.

(grammar) Dual.