WordNet sense 1 (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):

promethium

WordNet sense 2 (the person who holds the position of head of the government in England):

premier, Prime Minister

WordNet sense 3 (modulation of the phase of the carrier wave):

phase modulation

WordNet sense 4 (between noon and midnight):

p.m., post meridiem

WordNet sense 5 (after noon):

postmeridian

WordNet sense 6 (an examination and dissection of a dead body to determine cause of death or the changes produced by disease):

autopsy, postmortem, necropsy, postmortem examination, post-mortem examination, post-mortem