safety nut vs locknut

safety nut and locknut both are nouns.

Word	Noun	Adjective	Verb	Adverb
safety nut	Yes	No	No	No
locknut	Yes	No	No	No

As nouns, safety nut and locknut are synonyms defined as:

safety nut and locknut: supplementary nut that is screwed down on a primary nut to prevent it from loosening

safety nut (noun)	locknut (noun)
supplementary nut that is screwed down on a primary nut to prevent it from loosening	supplementary nut that is screwed down on a primary nut to prevent it from loosening