tractor trailer vs trailer truck

tractor trailer and trailer truck both are nouns.

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

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

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

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

tractor trailer (noun)	trailer truck (noun)
a truck consisting of a tractor and trailer together	a truck consisting of a tractor and trailer together