wrecker vs motortruck

wrecker and motortruck both are nouns.

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

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

wrecker: a truck equipped to hoist and pull wrecked cars (or to remove cars from no-parking zones)
motortruck: an automotive vehicle suitable for hauling

Other hypernyms of wrecker include truck.

wrecker (noun)	motortruck (noun)
a truck equipped to hoist and pull wrecked cars (or to remove cars from no-parking zones)	an automotive vehicle suitable for hauling
someone who commits sabotage or deliberately causes wrecks
someone who demolishes or dismantles buildings as a job