slime mould vs slime mold

slime mould and slime mold both are nouns.

Word	Noun	Adjective	Verb	Adverb
slime mould	Yes	No	No	No
slime mold	Yes	No	No	No

As nouns, slime mould and slime mold are synonyms defined as:

slime mould and slime mold: a naked mass of protoplasm having characteristics of both plants and animals; sometimes classified as protoctists

slime mould (noun)	slime mold (noun)
a naked mass of protoplasm having characteristics of both plants and animals; sometimes classified as protoctists	a naked mass of protoplasm having characteristics of both plants and animals; sometimes classified as protoctists