tractor trailer vs trucking rig

tractor trailer and trucking rig both are nouns.

Word	Noun	Adjective	Verb	Adverb
tractor trailer	Yes	No	No	No
trucking rig	Yes	No	No	No

As nouns, tractor trailer and trucking rig are synonyms defined as:

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

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

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