trojan vs trojan horse

trojan and trojan horse both are nouns.

Word	Noun	Adjective	Verb	Adverb
trojan	Yes	No	No	No
trojan horse	Yes	No	No	No

As nouns, trojan and trojan horse are synonyms defined as:

trojan and trojan horse: a program that appears desirable but actually contains something harmful

trojan (noun)	trojan horse (noun)
a program that appears desirable but actually contains something harmful	a program that appears desirable but actually contains something harmful