The Collaborative International Dictionary
Postmeridian
Postmeridian \Post`me*rid"i*an\, a. [L. postmeridianus; post after + meridianus. See Meridian.]
Coming after the sun has passed the meridian; being in, or belonging to, the afternoon. (Abbrev. P. M.)
Fig., belonging to the after portion of life; late. [R.]
Wiktionary
postmeridian
a. of or pertaining to the afternoon
WordNet
postmeridian
adj. after noon [ant: antemeridian]