eight•eenthPronunciation: (ā'tēnth'), [key]
next after the seventeenth; being the ordinal number for 18.
being one of 18 equal parts.
an eighteenth part, esp. of one (1/18
the eighteenth member of a series.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.