From WordNet (r) 3.0 (2006):
PM
n 1: an examination and dissection of a dead body to determine
cause of death or the changes produced by disease [syn:
autopsy, necropsy, postmortem, post-mortem, PM,
postmortem examination, post-mortem examination]
2: a soft silvery metallic element of the rare earth group
having no stable isotope; was discovered in radioactive form
as a fission product of uranium [syn: promethium, Pm,
atomic number 61]
3: the person who holds the position of head of the government
in the United Kingdom [syn: Prime Minister, PM,
premier]
4: modulation of the phase of the carrier wave [syn: phase
modulation, PM]