(Greek mythology) A mythological decade-long war and siege, ending in the destruction of Troy, which, as described in Homer's Iliad, was waged by a coalition of Achaeans (Greeks) led by King Agamemnon against the Trojans to avenge the abduction of Helen, wife of the Spartan King Menelaus, by Paris, son of the Trojan King Priam.

(Greek mythology) The hollow wooden horse by which the Greeks allegedly gained access to Ilium/Troy during the Trojan War.

(by extension) A subversive person or device placed within the ranks of the enemy. / (computer security) A malicious program that is disguised as legitimate software.

Alternative form of Trojan-horse

plural of Trojan horse

(astrophysics) a planet that occupies a Trojan point of a star system

(astrophysics) a pseudo-moon that occupies a Trojan point of a system

(astrophysics) the L4 and L5 Lagrange points of the Sun-Jupiter orbital configuration / (astrophysics) by extension, any L4 and L5 Lagrange points

(astrophysics) an asteroid occupying the Trojan points of the Sun-Jupiter system / (astrophysics) by extension, any asteroid occupying a Trojan point

plural of Trojan asteroid