trailer vs idler

trailer and idler both are nouns.

Word	Noun	Adjective	Verb	Adverb
trailer	Yes	No	No	No
idler	Yes	No	No	No

As nouns, idler is a hypernym of trailer; that is, idler is a word with a broader meaning than trailer:

trailer: someone who takes more time than necessary; someone who lags behind
idler: person who does no work

Other hypernyms of trailer include bum, do-nothing, layabout, loafer.

trailer (noun)	idler (noun)
a wheeled vehicle that can be pulled by a car or truck and is equipped for occupancy	person who does no work
a large transport conveyance designed to be pulled by a truck or tractor
an advertisement consisting of short scenes from a motion picture that will appear in the near future
someone who takes more time than necessary; someone who lags behind