I. noun
Usage: usually capitalized T
Etymology: so called from the gigantic and hollow wooden horse filled with soldiers by means of which the Greeks gained entrance into Troy during the Trojan War and insured the conquest of the city
1. : a device of placing espionage and propaganda agents inside the country of an intended victim for purposes of sabotage and direction of native subversive groups — compare fifth column
2. : a person, organization, or factor that is intended or likely to undermine an established institution
II. noun
Usage: usually capitalized T
: a seemingly useful computer program that contains concealed instructions which when activated at some later time perform an illicit or malicious action (as destroying data files) ; also : the concealed instructions of such a program — compare virus herein