giant sequoia vs big tree

giant sequoia and big tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
giant sequoia	Yes	No	No	No
big tree	Yes	No	No	No

As nouns, giant sequoia and big tree are synonyms defined as:

giant sequoia and big tree: extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism

Other synonyms of giant sequoia include Sequoia gigantea, Sequoia Wellingtonia, Sequoiadendron giganteum, Sierra redwood.

giant sequoia (noun)	big tree (noun)
extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism	extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism