trailer truck vs semi

trailer truck and semi both are nouns.

Word	Noun	Adjective	Verb	Adverb
trailer truck	Yes	No	No	No
semi	Yes	No	No	No

As nouns, trailer truck and semi are synonyms defined as:

trailer truck and semi: a truck consisting of a tractor and trailer together

Other synonyms of trailer truck include articulated lorry, rig, tractor trailer, trucking rig.

trailer truck (noun)	semi (noun)
a truck consisting of a tractor and trailer together	a trailer having wheels only in the rear; the front is supported by the towing vehicle
	a truck consisting of a tractor and trailer together
	one of the two competitions in the next to the last round of an elimination tournament