dumper vs motortruck

dumper and motortruck both are nouns.

Word	Noun	Adjective	Verb	Adverb
dumper	Yes	No	No	No
motortruck	Yes	No	No	No

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

dumper: truck whose contents can be emptied without handling; the front end of the platform can be pneumatically raised so that the load is discharged by gravity
motortruck: an automotive vehicle suitable for hauling

Other hypernyms of dumper include truck.

dumper (noun)	motortruck (noun)
truck whose contents can be emptied without handling; the front end of the platform can be pneumatically raised so that the load is discharged by gravity	an automotive vehicle suitable for hauling