PM vs post-mortem

PM and post-mortem both are nouns.

Word	Noun	Adjective	Verb	Adverb
PM	Yes	No	No	No
post-mortem	Yes	No	No	No

As nouns, PM and post-mortem are synonyms defined as:

PM and post-mortem: an examination and dissection of a dead body to determine cause of death or the changes produced by disease

PM (noun)	post-mortem (noun)
an examination and dissection of a dead body to determine cause of death or the changes produced by disease	an examination and dissection of a dead body to determine cause of death or the changes produced by disease
modulation of the phase of the carrier wave	discussion of an event after it has occurred
the person who holds the position of head of the government in the United Kingdom