truck vs trucking rig

truck and trucking rig both are nouns.

Word	Noun	Adjective	Verb	Adverb
truck	Yes	No	Yes	No
trucking rig	Yes	No	No	No

As nouns, trucking rig is a hyponym of truck; that is, trucking rig is a word with a more specific, narrower meaning than truck:

truck (noun)	trucking rig (noun)
an automotive vehicle suitable for hauling	a truck consisting of a tractor and trailer together
a handcart that has a frame with two low wheels and a ledge at the bottom and handles at the top; used to move crates or other heavy objects

truck (verb)	trucking rig (verb)
convey (goods etc.) by truck