machination vs secret plan

machination and secret plan both are nouns.

Word	Noun	Adjective	Verb	Adverb
machination	Yes	No	No	No
secret plan	Yes	No	No	No

As nouns, secret plan is a hypernym of machination; that is, secret plan is a word with a broader meaning than machination:

machination: a crafty and involved plot to achieve your (usually sinister) ends
secret plan: a secret scheme to do something (especially something underhand or illegal)

Other hypernyms of machination include game, plot.

machination (noun)	secret plan (noun)
a crafty and involved plot to achieve your (usually sinister) ends	a secret scheme to do something (especially something underhand or illegal)