moldboard vs mouldboard

moldboard and mouldboard both are nouns.

Word	Noun	Adjective	Verb	Adverb
moldboard	Yes	No	No	No
mouldboard	Yes	No	No	No

As nouns, moldboard and mouldboard are synonyms defined as:

moldboard and mouldboard: wedge formed by the curved part of a steel plow blade that turns the furrow

moldboard (noun)	mouldboard (noun)
wedge formed by the curved part of a steel plow blade that turns the furrow	wedge formed by the curved part of a steel plow blade that turns the furrow