p.m.

time from 12:00 noon to midnight, afternoon, time after noon; hours between noon and midnight

n. leader of an elected government, head of state

The 12-hour clock is a timekeeping convention in which the 24 hours of the day are divided into two periods called ante meridiem (a.m., from Latin, meaning "before mid day", or "before the middle of the day") and post meridiem (p.m., "after mid day" or "after the middle of the day"). Each period consists of 12 hours numbered 12 (acting as zero), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. Twelve o'clock is either noon or midnight.
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PM, Pm or pm can refer to: In Science:Post meridiem (also written P.M. and p.m.), Latin for "after noon" - this is used to disambiguate hours of the day, in the 12-hour clock systemParticulate matter, fine dust and soot suspended in the airPermanent magnetPetametre, a length unit (1015 m) (Pm)Perl modulePhase modulation, in electrical engineeringPicometre, a length unit (10-12 m) (pm)Pilot MonitoringPowdery mildew, a fungal disease that affects a wide range of plantspost mortemPrecious metalPrincipia Mathematica, in set theoryPromethium, in chemistry (Pm)
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Adverb
1. between noon and midnight; "let's meet at 8 P.M."
(synonym) post meridiem, PM
(classification) Latin

Adjective
1. after noon
(synonym) post meridiem, pm
(similar) postmeridian

for the record

P.M., post meridiem, between noon and midnight, in the afternoon, after the hour of 12:00 noon