tanker truck vs motortruck

tanker truck and motortruck both are nouns.

Word	Noun	Adjective	Verb	Adverb
tanker truck	Yes	No	No	No
motortruck	Yes	No	No	No

As nouns, motortruck is a hypernym of tanker truck; that is, motortruck is a word with a broader meaning than tanker truck:

tanker truck: a motor vehicle designed to carry liquefied loads, dry bulk cargo or gases on roads.
motortruck: an automotive vehicle suitable for hauling

Other hypernyms of tanker truck include truck.

tanker truck (noun)	motortruck (noun)
a motor vehicle designed to carry liquefied loads, dry bulk cargo or gases on roads.	an automotive vehicle suitable for hauling