Sequoia gigantea vs giant sequoia

Sequoia gigantea and giant sequoia both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sequoia gigantea	Yes	No	No	No
giant sequoia	Yes	No	No	No

As nouns, Sequoia gigantea and giant sequoia are synonyms defined as:

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

Other synonyms of Sequoia gigantea include big tree, Sequoia Wellingtonia, Sequoiadendron giganteum, Sierra redwood.

Sequoia gigantea (noun)	giant sequoia (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