field trip vs pleasure trip

field trip and pleasure trip both are nouns.

Word	Noun	Adjective	Verb	Adverb
field trip	Yes	No	No	No
pleasure trip	Yes	No	No	No

As nouns, pleasure trip is a hypernym of field trip; that is, pleasure trip is a word with a broader meaning than field trip:

field trip: a group excursion (to a museum or the woods or some historic place) for firsthand examination
pleasure trip: a journey taken for pleasure

Other hypernyms of field trip include excursion, expedition, jaunt, junket, outing, sashay.

field trip (noun)	pleasure trip (noun)
a group excursion (to a museum or the woods or some historic place) for firsthand examination	a journey taken for pleasure