garboard vs garboard plank

garboard and garboard plank both are nouns.

Word	Noun	Adjective	Verb	Adverb
garboard	Yes	No	No	No
garboard plank	Yes	No	No	No

As nouns, garboard and garboard plank are synonyms defined as:

garboard and garboard plank: the first wale laid next to the keel of a wooden ship

Other synonyms of garboard include garboard strake.

garboard (noun)	garboard plank (noun)
the first wale laid next to the keel of a wooden ship	the first wale laid next to the keel of a wooden ship